DOCSLIB.ORG

Implications of Prolonged Solar Minimum Conditions for the Space Debris Population

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Implications of Prolonged Solar Minimum Conditions for the Space Debris Population IMPLICATIONS OF PROLONGED SOLAR MINIMUM CONDITIONS FOR THE SPACE DEBRIS POPULATION Hugh G. Lewis(1) and Timothy Horbury(2) 8QLYHUVLW\RI6RXWKDPSWRQ$VWURQDXWLFV5HVHDUFK*URXS)DFXOW\RI(QJLQHHULQJDQGWKH(QYLURQPHQW 6RXWKDPSWRQ62%-8QLWHG.LQJGRP(PDLOKJOHZLV#VRWRQDFXN ,PSHULDO&ROOHJH/RQGRQ6SDFHDQG$WPRVSKHULF3K\VLFV*URXS'HSDUWPHQWRI3K\VLFV)DFXOW\RI1DWXUDO 6FLHQFHV/RQGRQ6:$=8QLWHG.LQJGRP(PDLOWKRUEXU\#LPSHULDODFXN 1 INTRODUCTION ABSTRACT The familiar solar sunspot cycle is a manifestation of a dynamo in the Sun’s interior, with the solar magnetic Observations of the current solar cycle show the likely field effectively flipping every 11 years. Low sunspot continuation of a long-term decline in solar activity that numbers – solar minimum – occur when the global field began during the 1980s. This decline could lead to is relatively dipolar-like, while solar maximum conditions similar to the Maunder minimum within 40 corresponds to a much more complex and variable field years [1], which would have consequences for the space configuration. debris environment. Solar activity is a key driver of atmospheric mass density and, subsequently, drag on Since the earliest systematic sunspot observations in the orbiting spacecraft and debris. Whilst several studies seventeenth century, it has become clear that the have investigated potential effects on the global climate, sunspot cycle is itself variable, both in period and no assessment has been made of the impact of a amplitude (Fig. 1). The most celebrated change in the Maunder-like minimum on the space debris population cycle is the Maunder minimum, from around 1645 to in Low Earth Orbit (LEO). Consequently, we present a 1700, when very few sunspots were observed. The new study of the future debris environment under weaker Dalton minimum, from around 1790 to 1830, Maunder minimum conditions and provide an comprised a set of cycles with sunspot maxima assessment of the possible consequences to the LEO significantly lower than those around them. space debris population and space operations. More recently, approximately coinciding with the start The University of Southampton’s Debris Analysis and of the Space Age, the Sun entered a period of enhanced Monitoring Architecture to the Geosynchronous activity known as a Grand Solar Maximum. Since the Environment (DAMAGE) has been used to analyse the mid-1980’s, however, activity levels have reduced. The consequences of a Maunder minimum of approximately minimum before the start of the current Cycle 24 was 50 years duration and to quantify the impact on the longer than expected and as the sun approaches its effectiveness of debris mitigation measures. Results maximum, the cycle is much weaker than those from these studies suggest an increase in collision immediately preceding it, suggesting a continued activity and a corresponding, rapid growth of the debris decline (see [1] for a recent review). Indeed, there is population during a Maunder minimum period, in spite some evidence from helioseismology measurements of on-going mitigation efforts. In the best case, the (e.g. [2]) that precursors of the next cycle within the DAMAGE results suggest that the population of debris solar interior are also weaker than at this point in the > 10 cm could double in number by the end of Maunder cycle, suggesting that Cycle 25 might be weaker again. minimum conditions. However, the rapid growth in the Solar cycle changes in its magnetic field have effects population is followed by a strong recovery period on elsewhere, for example in modulating the cosmic ray exit from a Maunder minimum. The recovery is flux at the Earth as a result of alterations in the characterised by a decrease in the debris population, interplanetary magnetic field. This makes it possible to which can be to a level similar to that seen before the use secondary measurements, such as cosmogenic onset of the Maunder minimum, if mitigation efforts are isotope production, to extend estimates of solar activity sustained. As such, prolonged solar minimum conditions levels beyond the earliest systematic sunspot may have relatively benign implications for the long- observations. Such reconstructions show that solar term evolution of the debris environment. However, the activity levels are indeed variable over a range of scales, risks to spacecraft from collisions with debris during a that the Sun can enter an extended period of low Maunder-like minimum would be considerably higher activity, such as the Maunder minimum, after a Grand than present, and exacerbated by any deficiency in Solar Maximum and that this occurs after around 1 in debris mitigation efforts, with corresponding impacts on 10 of such maxima [3]. space operations. _____________________________________ Proc. ‘6th European Conference on Space Debris’ Darmstadt, Germany, 22–25 April 2013 (ESA SP-723, August 2013) It is therefore unlikely but not impossible that the Sun is Atmospheric decay remains the only effective sink in the process of entering a low activity state, similar to mechanism for space debris up to altitudes of about 600 the Maunder or Dalton minima. If such a change, km. The drag acceleration, D', on a satellite with unprecedented since the beginning of the Space Age, cross-sectional area $ and mass 0 is a linear function of were to occur, it would have significant effects on the the local mass density, U, space environment of the Earth and near-Earth space, 1 $ (1) 2 , for example in enhanced cosmic ray flux. It would also D' &' UYU reduce the F10.7 EUV flux incident on the Earth’s 2 0 atmosphere, and through lowered heating rates reduce where &' is the drag coefficient and YU is the velocity of drag on objects in Low Earth Orbit. Such a reduction in the satellite relative to the atmosphere. A decrease in drag could increase the orbital debris population and mass density will, thus, produce a corresponding hence increase the risk to operational assets. decrease in the drag acceleration on a satellite, leading to an increase in the orbital lifetime. Solar irradiance is a key driver of mass density change in the thermosphere. Changes in solar irradiance over the 11 year solar cycle cause corresponding mass density changes of up to an order of magnitude [5]. These changes in density cause large variations in atmospheric drag, from (1), and the rate at which orbiting objects re-enter the atmosphere. )LJXUH \HDUV RI 6XQVSRW REVHUYDWLRQV ,PDJH In DAMAGE, the total mass density and density scale FUHDWHG E\ 5REHUW $ 5RKGH *OREDO :DUPLQJ $UW height are stored as look-up tables for discrete altitudes KWWSZZZJOREDOZDUPLQJDUWFRPZLNL)LOH6XQVSRWB1 and exospheric temperatures. Log linear interpolation is XPEHUVBSQJ used to extract density and scale height estimates from the look-up tables at the perigees of all objects within 2 THE DAMAGE MODEL the LEO region for )10.7(W) values throughout the projection period. The exospheric temperature, 7H[(W), at The Debris Analysis and Monitoring Architecture to the time W is Geosynchronous Environment (DAMAGE) is a three- , (2) dimensional computational model of the full LEO to 7H[ W 1.125 379 >3.24)10.7 W @ 59.89 '7H[ W GEO debris environment. It includes source models for objects down to 10 cm but is capable of evolving where )10.7(W) is the solar flux at a wavelength of 10.7 populations of objects down to 1 mm. cm and '7H[(W) is a correction factor for the semi-annual variability. The constant (59.89) is a correction due for DAMAGE is supported by a fast, semi-analytical orbital geomagnetic activity, which is based on a 20-year propagator, a breakup model, several collision average represented by Kp = 2.13. Projected solar prediction algorithms including a method based on the activity is described in DAMAGE typically using a CUBE approach adopted in NASA’s LEO-to-GEO pseudo-sinusoidal model, but has been modified for this Environment Debris model (LEGEND) [4], and a work to account for a prolonged period of low solar satellite failure model, which accounts for mission activity. failures resulting from the non-catastrophic impacts of small particles. Projections into the future are typically 2.2 DAMAGE Collision Probability performed using a Monte Carlo (MC) approach to Estimation account for stochastic elements within the model and to establish reliable statistics. DAMAGE normally uses an approach based on NASA’s CUBE algorithm [6] for predicting collision 2.1 DAMAGE Orbital Propagator risk. The advantage of this approach is that it involves a simple calculation and scales linearly with the number The DAMAGE orbital propagator includes orbital of objects. Whilst the implementation developed by perturbations due to Earth gravity harmonics (J2, J3, and NASA assumes a non-zero collision probability only for J2,2), luni-solar gravitational perturbations, solar objects residing within the same “cube”, the DAMAGE radiation pressure and atmospheric drag. The drag algorithm ensures that all close approaches within a model assumes a rotating, oblate atmosphere with high- user-specified distance from a target are identified and altitude winds. Atmospheric density and density scale analysed. This is achieved, essentially, by calculating height values are taken from the 1972 COSPAR the position of the target and the debris in a geo-centric International Reference Atmosphere (CIRA), which Cartesian coordinate system and then by “binning” the includes semi-annual and diurnal variations. values in the x-, y- and z-directions. The aim is then to identify all cases where a target spacecraft and a debris V 6 6 2 6 6 (4) particle reside in the same cube bin [6]. By expanding 7 ' 7 ' the search to include cases where a target spacecraft and for a target area, 67, and a debris area, 6', assuming debris reside in neighbouring cubes – in Cartesian both objects to be spherical. The calculation of collision space, there are eight neighbouring cubes – and then probability assumes that the target object can reside at applying a distance constraint, the DAMAGE approach any point within the cube volume with uniform identifies all cases where a target spacecraft and a debris probability.
Load more

Recommended publications
  • → Investigating Solar Cycles a Soho Archive & Ulysses Final Archive Tutorial
    → INVESTIGATING SOLAR CYCLES A SOHO ARCHIVE & ULYSSES FINAL ARCHIVE TUTORIAL SCIENCE ARCHIVES AND VO TEAM Tutorial Written By: Madeleine Finlay, as part of an ESAC Trainee Project 2013 (ESA Student Placement) Tutorial Design and Layout: Pedro Osuna & Madeleine Finlay Tutorial Science Support: Deborah Baines Acknowledgements would like to be given to the whole SAT Team for the implementation of the Ulysses and Soho archives http://archives.esac.esa.int We would also like to thank; Benjamín Montesinos, Department of Astrophysics, Centre for Astrobiology (CAB, CSIC-INTA), Madrid, Spain for having reviewed and ratified the scientific concepts in this tutorial. CONTACT [email protected] [email protected] ESAC Science Archives and Virtual Observatory Team European Space Agency European Space Astronomy Centre (ESAC) Tutorial → CONTENTS PART 1 ....................................................................................................3 BACKGROUND ..........................................................................................4-5 THE EXPERIMENT .......................................................................................6 PART 1 | SECTION 1 .................................................................................7-8 PART 1 | SECTION 2 ...............................................................................9-11 PART 2 ..................................................................................................12 BACKGROUND ........................................................................................13-14
    [Show full text]
  • Riley Et Al., 2015
    The Astrophysical Journal, 802:105 (14pp), 2015 April 1 doi:10.1088/0004-637X/802/2/105 © 2015. The American Astronomical Society. All rights reserved. INFERRING THE STRUCTURE OF THE SOLAR CORONA AND INNER HELIOSPHERE DURING THE MAUNDER MINIMUM USING GLOBAL THERMODYNAMIC MAGNETOHYDRODYNAMIC SIMULATIONS Pete Riley1, Roberto Lionello1, Jon A. Linker1, Ed Cliver2, Andre Balogh3, Jürg Beer4, Paul Charbonneau5, Nancy Crooker6, Marc DeRosa7, Mike Lockwood8, Matt Owens8, Ken McCracken9, Ilya Usoskin10, and S. Koutchmy11 1 Predictive Science, 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121, USA; [email protected], [email protected], [email protected] 2 National Solar Observatory, Sunspot, NM 88349, USA; [email protected] 3 Imperial College, South Kensington Campus, Department of Physics, Huxley Building 6M68, London, SW7 2AZ, UK; [email protected] 4 Surface Waters, Eawag, Ueberlandstrasse 133, P.O. Box 611, 8600 Duebendorf, Switzerland; [email protected] 5 Département de Physique, Université de Montréal, C.P. 6128 Centre-Ville, Montréal, Qc, H3C-3J7, Canada; [email protected] 6 Center for Space Physics, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA; [email protected] 7 Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover St., B/252, Palo Alto, CA 94304, USA; [email protected] 8 University of Reading, Department of Meteorology, Reading, Berkshire, RG6 6BB, UK; [email protected], [email protected] 9 100 Mt. Jellore Lane, Woodlands, NSW, 2575, Australia; [email protected] 10 Sodankyla Geophysical Observatory, FIN-90014, University of Oulu, Finland; ilya.usoskin@oulu.fi 11 Institut d’Astrophysique de Paris, CNRS and UPMC, Paris, France; [email protected] Received 2014 September 29; accepted 2015 January 29; published 2015 March 30 ABSTRACT Observations of the Sun’s corona during the space era have led to a picture of relatively constant, but cyclically varying solar output and structure.
    [Show full text]
  • Level and Length of Cyclic Solar Activity During the Maunder Minimum As Deduced from the Active-Day Statistics
    A&A 577, A71 (2015) Astronomy DOI: 10.1051/0004-6361/201525962 & c ESO 2015 Astrophysics Level and length of cyclic solar activity during the Maunder minimum as deduced from the active-day statistics J. M. Vaquero1,G.A.Kovaltsov2,I.G.Usoskin3, V. M. S. Carrasco4, and M. C. Gallego4 1 Departamento de Física, Universidad de Extremadura, 06800 Mérida, Spain 2 Ioffe Physical-Technical Institute, 194021 St. Petersburg, Russia 3 Sodankylä Geophysical Observatory and ReSoLVE Center of Excellence, University of Oulu, 90014 Oulu, Finland e-mail: [email protected] 4 Departamento de Física, Universidad de Extremadura, 06071 Badajoz, Spain Received 25 February 2015 / Accepted 25 March 2015 ABSTRACT Aims. The Maunder minimum (MM) of greatly reduced solar activity took place in 1645–1715, but the exact level of sunspot activity is uncertain because it is based, to a large extent, on historical generic statements of the absence of spots on the Sun. Using a conservative approach, we aim to assess the level and length of solar cycle during the MM on the basis of direct historical records by astronomers of that time. Methods. A database of the active and inactive days (days with and without recorded sunspots on the solar disc) is constructed for three models of different levels of conservatism (loose, optimum, and strict models) regarding generic no-spot records. We used the active day fraction to estimate the group sunspot number during the MM. Results. A clear cyclic variability is found throughout the MM with peaks at around 1655–1657, 1675, 1684, 1705, and possibly 1666, with the active-day fraction not exceeding 0.2, 0.3, or 0.4 during the core MM, for the three models.
    [Show full text]
  • The Maunder Minimum and the Variable Sun-Earth Connection
    The Maunder Minimum and the Variable Sun-Earth Connection (Front illustration: the Sun without spots, July 27, 1954) By Willie Wei-Hock Soon and Steven H. Yaskell To Soon Gim-Chuan, Chua Chiew-See, Pham Than (Lien+Van’s mother) and Ulla and Anna In Memory of Miriam Fuchs (baba Gil’s mother)---W.H.S. In Memory of Andrew Hoff---S.H.Y. To interrupt His Yellow Plan The Sun does not allow Caprices of the Atmosphere – And even when the Snow Heaves Balls of Specks, like Vicious Boy Directly in His Eye – Does not so much as turn His Head Busy with Majesty – ‘Tis His to stimulate the Earth And magnetize the Sea - And bind Astronomy, in place, Yet Any passing by Would deem Ourselves – the busier As the Minutest Bee That rides – emits a Thunder – A Bomb – to justify Emily Dickinson (poem 224. c. 1862) Since people are by nature poorly equipped to register any but short-term changes, it is not surprising that we fail to notice slower changes in either climate or the sun. John A. Eddy, The New Solar Physics (1977-78) Foreword By E. N. Parker In this time of global warming we are impelled by both the anticipated dire consequences and by scientific curiosity to investigate the factors that drive the climate. Climate has fluctuated strongly and abruptly in the past, with ice ages and interglacial warming as the long term extremes. Historical research in the last decades has shown short term climatic transients to be a frequent occurrence, often imposing disastrous hardship on the afflicted human populations.
    [Show full text]
  • 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.
    [Show full text]
  • Solar Orbiter and Sentinels
    HELEX: Heliophysical Explorers: Solar Orbiter and Sentinels Report of the Joint Science and Technology Definition Team (JSTDT) PRE-PUBLICATION VERSION 1 Contents HELEX Joint Science and Technology Definition Team .................................................................. 3 Executive Summary ................................................................................................................................. 4 1.0 Introduction ........................................................................................................................................ 6 1.1 Heliophysical Explorers (HELEX): Solar Orbiter and the Inner Heliospheric Sentinels ........ 7 2.0 Science Objectives .............................................................................................................................. 8 2.1 What are the origins of the solar wind streams and the heliospheric magnetic field? ............. 9 2.2 What are the sources, acceleration mechanisms, and transport processes of solar energetic particles? ........................................................................................................................................ 13 2.3 How do coronal mass ejections evolve in the inner heliosphere? ............................................. 16 2.4 High-latitude-phase science ......................................................................................................... 19 3.0 Measurement Requirements and Science Implementation ........................................................ 20
    [Show full text]
  • 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.
    [Show full text]
  • Can You Spot the Sunspots?
    Spot the Sunspots Can you spot the sunspots? Description Use binoculars or a telescope to identify and track sunspots. You’ll need a bright sunny day. Age Level: 10 and up Materials • two sheets of bright • Do not use binoculars whose white paper larger, objective lenses are 50 • a book mm or wider in diameter. • tape • Binoculars are usually described • binoculars or a telescope by numbers like 7 x 35; the larger • tripod number is the diameter in mm of • pencil the objective lenses. • piece of cardboard, • Some binoculars cannot be easily roughly 30 cm x 30 cm attached to a tripod. • scissors • You might need to use rubber • thick piece of paper, roughly bands or tape to safely hold the 10 cm x 10 cm (optional) binoculars on the tripod. • rubber bands (optional) Time Safety Preparation: 5 minutes Do not look directly at the sun with your eyes, Activity: 15 minutes through binoculars, or through a telescope! Do not Cleanup: 5 minutes leave binoculars or a telescope unattended, since the optics can be damaged by too much Sun exposure. 1 If you’re using binoculars, cover one of the objective (larger) lenses with either a lens cap or thick piece of folded paper (use tape, attached to the body of the binoculars, to hold the paper in position). If using a telescope, cover the finderscope the same way. This ensures that only a single image of the Sun is created. Next, tape one piece of paper to a book to make a stiff writing surface. If using binoculars, trace both of the larger, objective lenses in the middle of the piece of cardboard.
    [Show full text]
  • The 2015 Senior Review of the Heliophysics Operating Missions
    The 2015 Senior Review of the Heliophysics Operating Missions June 11, 2015 Submitted to: Steven Clarke, Director Heliophysics Division, Science Mission Directorate Jeffrey Hayes, Program Executive for Missions Operations and Data Analysis Submitted by the 2015 Heliophysics Senior Review panel: Arthur Poland (Chair), Luca Bertello, Paul Evenson, Silvano Fineschi, Maura Hagan, Charles Holmes, Randy Jokipii, Farzad Kamalabadi, KD Leka, Ian Mann, Robert McCoy, Merav Opher, Christopher Owen, Alexei Pevtsov, Markus Rapp, Phil Richards, Rodney Viereck, Nicole Vilmer. i Executive Summary The 2015 Heliophysics Senior Review panel undertook a review of 15 missions currently in operation in April 2015. The panel found that all the missions continue to produce science that is highly valuable to the scientific community and that they are an excellent investment by the public that funds them. At the top level, the panel finds: • NASA’s Heliophysics Division has an excellent fleet of spacecraft to study the Sun, heliosphere, geospace, and the interaction between the solar system and interstellar space as a connected system. The extended missions collectively contribute to all three of the overarching objectives of the Heliophysics Division. o Understand the changing flow of energy and matter throughout the Sun, Heliosphere, and Planetary Environments. o Explore the fundamental physical processes of space plasma systems. o Define the origins and societal impacts of variability in the Earth/Sun System. • All the missions reviewed here are needed in order to study this connected system. • Progress in the collection of high quality data and in the application of these data to computer models to better understand the physics has been exceptional.
    [Show full text]
  • Coronal Mass Ejections and Solar Radio Emissions
    CORONAL MASS EJECTIONS AND SOLAR RADIO EMISSIONS N. Gopalswamy∗ Abstract Three types of low-frequency nonthermal radio bursts are associated with coro- nal mass ejections (CMEs): Type III bursts due to accelerated electrons propagating along open magnetic field lines, type II bursts due to electrons accelerated in shocks, and type IV bursts due to electrons trapped in post-eruption arcades behind CMEs. This paper presents a summary of results obtained during solar cycle 23 primarily using the white-light coronagraphic observations from the Solar Heliospheric Ob- servatory (SOHO) and the WAVES experiment on board Wind. 1 Introduction Coronal mass ejections (CMEs) are associated with a whole host of radio bursts caused by nonthermal electrons accelerated during the eruption process. Radio bursts at low frequencies (< 15 MHz) are of particular interest because they are associated with ener- getic CMEs that travel far into the interplanetary (IP) medium and affect Earth’s space environment if Earth-directed. Low frequency radio emission needs to be observed from space because of the ionospheric cutoff (see Fig. 1), although some radio instruments permit observations down to a few MHz [Erickson 1997; Melnik et al., 2008]. Three types of radio bursts are prominent at low frequencies: type III, type II, and type IV bursts, all due to nonthermal electrons accelerated during solar eruptions. The radio emission is thought to be produced by the plasma emission mechanism [Ginzburg and Zheleznyakov, 1958], involving the generation of Langmuir waves by nonthermal electrons accelerated during the eruption and the conversion of Langmuir waves to electromagnetic radiation. Langmuir waves scattered off of ions or low-frequency turbulence result in radiation at the fundamental (or first harmonic) of the local plasma frequency.
    [Show full text]
  • Galactic Cosmic Ray Radiation Hazard in the Unusual Extended Solar Minimum Between Solar Cycle 23 and 24
    1 Galactic Cosmic Ray Radiation Hazard in the Unusual Extended Solar 2 Minimum between Solar Cycle 23 and 24 3 4 N. A. Schwadron, A. J. Boyd, K. Kozarev 5 Boston University, Boston, Mass, USA 6 M. Golightly, H. Spence 7 University of New Hampshire, Durham New Hampshire, USA 8 L. W. Townsend 9 University of Tennessee, Knoxville, TN, USA 10 M. Owens 11 Space Environment Physics Group, Department of Meteorology, University of Reading, 12 UK 13 14 Abstract. Galactic Cosmic Rays (GCRs) are extremely difficult to shield against and 15 pose one of most severe long-term hazards for human exploration of space. The recent 16 solar minimum between solar cycle 23 and 24 shows a prolonged period of reduced solar 17 activity and low interplanetary magnetic field strengths. As a result, the modulation of 18 GCRs is very weak, and the fluxes of GCRs are near their highest levels in the last 25 19 years in the Fall of 2009. Here, we explore the dose-rates of GCRs in the current 20 prolonged solar minimum and make predictions for the Lunar Reconnaissance Orbiter 21 (LRO) Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which is now 22 measuring GCRs in the lunar environment. Our results confirm the weak modulation of 23 GCRs leading to the largest dose rates seen in the last 25 years over a prolonged period of 24 little solar activity. 25 26 Background – Galactic Cosmic Rays and Human Health 27 28 In balloon flights in 1912-1913, Hess first measured a form of radiation that intensified 29 with altitude [Hess, 1912; 1913].
    [Show full text]
  • The Sun-Climate Connection John A
    The Sun-Climate Connection John A. Eddy National Solar Observatory Tucson, Arizona Surely the oldest of all suspected solar-terrestrial connections—and by far the most important in terms of potential societal impacts—are probable links between solar variations and regional or global climate. Dramatic advances in recent years in both solar physics and in climatology have moved this age-old question out of the closet and into the light of more rigorous tests and examination. They also allow us to frame it more clearly in the context of other, competing or interactive climate change mechanisms. For the Sun, these advances include, among others, the results from a quarter century of radiometric monitoring of solar irradiance from space; the exploitation of naturally-sequestered cosmogenic isotope records to extend the known history of solar activity hundreds of thousands of years into the past; and success in defining the impacts of variations in solar ultraviolet radiation on stratospheric chemistry and dynamics. Similar seminal advances in what we know of climate and climatic change include vast improvements in our knowledge of the interactive climate system and in our ability to model and test possible forcing mechanisms; and the recovery and accumulation of longer and more extensive records of environmental changes of the past. In 2003, the NASA Living With a Star Program commissioned an interdisciplinary Task Group, which I chaired, to consider what is now known or suspected of the effects of solar variations on terrestrial climate; to frame the outstanding questions that currently limit progress; and to define current needs in Sun- Climate research.
    [Show full text]