The Canonical Sunspot Cycle

Sunspots are indicators of other phenomena that can be important to space weather, and ultimately to ionospheric effects on telecommunication systems. Actually, sunspots are probably overrated as indicators of space weather phenomena. Nevertheless, sunspots have been monitored for centuries and have proved to be a useful if imprecise index. Indeed, because of its historical record and availability, most predictive models are at least partly based upon some measure of the sunspot number. The...

Refraction

Ionospheric refraction and group path delay errors are especially important for radar ranging and surveillance problems. The last row in Table 4-8 indicates the amount of wedge refraction that is introduced as a radiowave penetrates the troposphere and then traverses the ionosphere. Figure 4-8 gives the geometry. Table 4-8 Effects Related to the Electron Content Table 4-8 Effects Related to the Electron Content Note The units of EC are electrons m2, and Hl is that component of the geomagnetic...

General Properties Of The Ionosphere 321 Basic Structure

The ionosphere is an ionized region in the upper atmosphere that, by generally accepted convention, lies between an altitude range of 60-1000 kilometers. Nevertheless the region above 1000 kilometers but below 2000 kilometers, called the protonosphere, is also ionized and may be an important region when considering the totality of ionization effects on radio systems. As a matter of convenience, some specialists have combined the ionosphere and protonosphere into a single region of ionization....

Medium Frequency

Some treatments group Medium Frequency (MF) and High Frequency (HF) together since both may utilize the skywave mode of propagation, and, with the possible exception of the lower MF band, operational utility is usually achieved through exploitation of this mode. Additionally, both MF and HF exhibit useful groundwave properties. For example, large-scale D-region absorption events, such as PCA or SWF, will reduce the competing noise at the groundwave receiver terminal arriving by skywave. Hence,...

Ionospheric Response To Solar Flares

Now we shall take note of a special class of effects called Sudden Ionospheric Disturbances (SID). These constitute those events that arise as a result of the atmospheric interaction with electromagnetic flux from solar flares. A book by Mitra 1974 is an excellent treatise on the ionospheric effects of solar flares. We recognize that the sun is the ultimate source for a large variety of ionospheric and magnetospheric effects. Figure 3-24 exhibits the hierarchy of solar-induced ionospheric...

Geomagnetic Activity Indices

Indices are useful for empirical modeling as well as for forecasting because they provide a convenient parameter set that may be used for driving the model. We have seen that sunspot number Rl2 or the flux index < > 2 are convenient, if not totally representative, of solar activity. The magnetic activity also lends itself to the development of a wide range of index representations. Moreover, the magnetic activity indices are organized and smoothed in a variety of ways that may have the...

The Ionospheric Storm

The magnetic storm is a fascinating geophysical phenomenon, which goes far beyond the visible evidence corresponding to auroral displays at high latitudes. It is central to the issues surrounding what is now referred to as space weather. A discourse on this subject is beyond the scope of this chapter, but the reader is referred to an excellent geophysical monograph edited by Tsurutani et al. 1997 , Current understandings about the ionospheric storm processes appear in a paper by Buosanto 2000 ....

The Halloween Storm Period of 2003

As noted in Section 2.2.8, The October 2003 period was an extraordinary period of significant solar activity. Region 486 produced two enormous x-ray flares, with accompanying CMEs, on 28 and 29 October, 2003. The amplitudes of the flares were XI7 and XI0 respectively as depicted in Figure 2-13. Extreme (i.e., G5) magnetic storms were introduced following impact of both of the CMEs. The second storm has since been termed the Halloween storm in view of its coincidence with the well-known holiday,...

Equilibrium Processes

The equation that expresses the time rate of change of electron concentration, Ne, is the continuity equation dNe dt q- L(Ne) - div (Ne V) (3.6) where Ne is the electron density, IJN,,) is the loss rate, which is dependent upon the electron density, div stands for the vector divergence operator, and V is the electron drift velocity. 0.01 0.02 0.05 0.1 0.2 0.5 1 q(Z) qe 0.1 0.15 0.2 0.3 0.4 0.6 0.8 N(Z) Ne Figure 3-6 Rate of electron production as a function of reduced height (h-h ) and for...

Outline Of Ionospheric Effects

The ionosphere is a partially ionized region of the upper atmosphere loosely partitioned into three major regions termed D, E, and F. It extends from roughly 50 km to 2000 km in altitude as defined by its sensible effect upon radiowave propagation systems. The reader is referred to Figure 3-1 in the last chapter. Although only a cartoon, the figure is still instructive. It depicts the layering properties of the midlatitude ionosphere for both daytime and nighttime conditions, and these...

Active Regions Coronal Holes and the Solar Wind

Active areas on the sun are the regions where there arise many phenomena whose form depends upon the region of the spectrum being monitored. Sunspots are best observed in the visible wavelengths, whereas disturbances in the coronal area overlying the disk are best examined in the soft x-ray band with satellite or rocket-borne instruments that are not affected by atmospheric absorption. X-ray emissions are not observable at ground level, and white light observations of the tenuous corona are...

Storms and Declining Solar Activity

Figure 2-12, corresponding to solar cycle 19, suggests that ionospheric storms have a peak following the maximum in sunspot number. This is evidently a general statement. Still, to this day, the popular view within the public at-large, as well as some otherwise well-informed telecommunication specialists, is that the sunspot maximum period is all important. The myth that the peak of the smoothed sunspot cycle is the only thing that matters was surely broken in the latter half of 2003, a period...

The Geomagnetic Field

Geomagnetic Coordinates

To obtain an understanding of the magnetosphere, we must first examine the geomagnetic Field. The earth's magnetic field is an important feature since it generally prevents a direct encounter between the ionosphere and energetic particles of solar origin, and especially solar wind. Mars, for example, does not have a magnetosphere, and it is widely held that solar wind erosion has eliminated a good portion of the Martian atmosphere. A geographically localized region that does not afford this...

The Noaasec Storm Model

It is known that the ionosphere behaves quite differently from storm-to-storm, certainly with respect to the details, and there are latitudinal, seasonal, diurnal and solar epochal effects to consider. Moreover, it makes a difference whether the onset of the storm is during the day and during the night. Empirical models are data-driven but most efforts rely upon physical insight to extrapolate results into those domains for which data are sparse or unavailable altogether. Empirical models of...

Space Weather Support For Systems 451 Military C3I Requirements

As has been inferred throughout this monograph, military requirements have dominated the development of operational systems that incorporate space weather information, either actively or passively. In Table 4-9 is a listing of telecommunication disciplines that are influenced or even controlled by the ionosphere and its variations. The ionospheric variability is, of course, a manifestation of space weather. Other military mission areas include missile warning, and the dissemination of weather...

Longwave Propagation General Remarks

It is worth noting that the investigation of longwave propagation (from ELF through LF) was greatly influenced by ground-based observation of whistlers, a mode of propagation that is strongly influenced by the earth's magnetic field. This mode allows ionospheric penetration but no major system application of this mode has been developed. However, a number of proposals have recently been made for which longwave transmitters would be orbited, providing longwave terrestrial coverage from space....

Formation of Midlatitude Sporadic E

It has been suggested that wind shears in the upper atmosphere are responsible for the formation of sporadic E at midlatitudes. We shall review this process briefly. It should be recalled from examination of photochemistry in the ionosphere that molecular ions such as those, which exist in the E region, introduce relatively rapid electron loss by recombination. At the same time it is recognized that an enormous number of meteors burn up in the E region. This meteoric debris is largely comprised...

Ionospheric Modeling Panel at IES2002

Author's Note I have had the good fortune to organize the triennial Ionospheric Effects Symposia since 1975, and the event in 2002 included a special forum on Ionospheric Models-Current and Future . The Forum was ably chaired by Dr. Ken Davies of NOAA (retired) and Dr. Anthea Coster (MIT-Lincoln Lab, now MIT-Haystack Observatory). The panel co-chairs developed a full summary that is contained in the Proceedings of IES2002. It turned out to be a rather interesting forum, and I felt it would be...

Solar Variability

The solar electromagnetic and particulate flux reaching the earth exhibits considerable short-term variability, and the (long-term) time-averaged behavior tracks the general tendency, but not the detailed morphology, of solar active regions and sunspots. This narrow bandwidth behavior is well known. As one increases the bandwidth of the observational filter, we begin to see more irregular behavior. Indeed, in the time domain, the temporal variability ranges from minutes to years. Table 2-3...

Data Assimilation and Kalman Filters

As a practical matter, there is a natural tendency to trust data over theory if there is some assurance that the data truly represents the quantity being observed. In practice, data is obtained from measurements by imperfect instruments against a background of noise and other factors that may camouflage the true values be sought. Even if we are convinced that the data is of high quality, the application of multi-station data in development of an ionospheric map can be problematic for a variety...

Chapman Layer Theory

Chapman Layer

One of the basic tenets of Chapman theory is that solar radiation will penetrate to an altitude for which the total number of atoms or molecules P (populating a column of unit cross sectional area directed toward the sun) is equal to the inverse of the absorption (or interaction) cross section a. In other words P I a . The peak in ionization will be produced in the neighborhood of that altitude, and the concept is valid for oblique solar illumination as well as for the case in which the sun is...

Telecommunication Systems 41 Introduction

Ionosphere Telecommunication

Much of this chapter is based upon earlier work Goodman and Aarons, 1990 published just prior to the peak of solar cycle 22. Since that time, many issues remain the same, but the growth in technology has led to different approaches. The expanded use of GPS within the civilian sector is but one example. Another change is the growth in capability to monitor and assess the real-time environment so that improved predictions can be entertained. But the Internet has arguably provided the most...

Description Of The Ionospheric Layers 341 Sounder Measurement Method

In any discussion of the ionospheric electron density distribution, it is important to recognize that many experimental methods have been used to arrive at our current understanding. The major ones include ground-based vertical incidence sounding (VIS), topside sounding using satellite platforms, incoherent backscatter radar, the Faraday rotation and signal delay of satellite signals, as well as in-situ measurements using rocket probes and satellites. The VIS method, which employs the High...

Ionospheric Doppler Shift

Ionospheric Doppler is given by the time rate of change of the ionospheric phase change times the quantity (l 2jt). In other words, simply divide Equation 4.4 by 2n. We then have the following Af -1.34(10 7)f-' d dt (EC) (4.6) This effect is not very significant if the transmission frequency is sufficiently high. For example, for a rapidly moving satellite, d dt (EC) would be order of the EC divided by several minutes. We assume d dt (EC) A(EC) At, where A(EC) and At are finite values. Taking...

An Historical Perspective

The author is not an historian, but he recognizes the benefit of retrospective examination of the great scientists, their achievements, and the role they play in the advance of space weather and communication technologies. A good deal of the information in this historical perspective is derived from the author's earlier book on HF Communication Science & Technology (i.e., Goodman 1991 ). Another excellent source is a series of articles in EOS by E.W. Cliver 1994a, 1994b, 1995 dealing with...

Short Term Variations

Total Electron Content Space Weather

Variations in layer critical frequencies will arise on an hour-to-hour and day-to-day basis, especially for the F2 region. Day-to-Day F region variability is exhibited in Figure 3-12 for a period of maximum solar activity and for midlatitudes. It appears that much of this variability owes its existence to the impact of geomagnetic storms, traveling ionospheric disturbances (TIDs), and miscellaneous F region dynamic effects. TIDs are one of the more fascinating features of the ionosphere. They...

European Union COST Action Models

The European Union has organized a number of activities under a program termed COST, which stands for Cooperation in Scientific and Technical Research, and specific Actions under COST have been sanctioned. The Actions are necessarily Eurocentric, although there are clearly certain developments that apply globally. Three of these COST Actions of relevance to ionospheric modeling, forecasting and telecommunication system effects have been designated as Actions 238, 251 and 271. An Action on Space...

Springer

Radio Propagation Services, Inc. (RPSI) Alexandria VA 22308-1943 Library of Congress Cataloging-in-Publication Data A C.I.P. Catalogue record for this book is available from the Library of Congress. Space Weather & Telecommunications John M. Goodman p.cm. (The Kluwer International Series in Engineering and Computer Science) Includes bibliographical references and index. ISBN 0-387-23670-8 (HC) ISBN 0-387-23671-6 (eBook) Printed on acid-free paper. 2005 Springer Science+Business Media, Inc....

The F2 Region

The F2 region is the most prominent layer in the ionosphere, and this significance arises as a result of its median height (the highest of all the component layers) and of course its dominant electron density. It is also characterized by large ensembles of irregularity scales AL and temporal variations AT . The F2 region is a vast zone which eludes prediction on the microscale (A L < 1 Km) and mesoscale (1 < AL < 1000 Km) levels, and even provides challenges to forecasters for global and...

Prediction of the Sunspot Cycle

All techniques used for long-term prediction of sunspots have significant error bars, and, because of this, the value of long-term predictions is questionable for any detailed propagation analysis or a meaningful evaluation of telecommunication impairments. While system performance assessment and system design factors both depend upon solar activity, long-term predictions are of more value in the latter instance. Other matters such as station-keeping, orbital decay probability, and spacecraft...

References

Aarons, J., 1977, Equatorial Scintillations A Review, IEEE Trans. Ant. Prop., 25, 729-736. Araujo-Pradere, E.T., T.J. Fuller-Rowell, and D. Bilitza, 2004, The STORM Response in IRI2000, and Challenges for Empirical Models of the Future, Radio Sci., 39, RS1S24, doi 10,1029 2002RS002805. Anderson B., and J. Moore, 1979, Optimal Filtering, Prentice-Hall. Anderson, D.N., M. Mendillo, and B. Herniter, 1987, A Semi-Empirical Low-Latitude Ionospheric Model, Radio Science, 22 292. Anderson, D.N., J.M....

System Performance Modeling

There are a number of HF system performance models (i.e., IONCAP, VOACAP, ICEPAC, ASAPS, and REC533) that can be used to assist in frequency management and related endeavors. There is an ITS-Boulder web site from which VOACAP, ICEPAC, and REC 533 may be downloaded. (Suggestion Go to the ITS website using your browser, click on radio propagation software, and then on HF models.) A detailed discussion of these and other models may be found in Chapter 5 of Goodman 1991 . The internationally...

Global Morphology of Scintillation

Region-specific examinations of the scintillation effect have been published for both high-latitude Basti et al., 1985 Weber et al., 1985 Aarons et al., 1988 Basu et al., 1988b , and equatorial latitude zones Basu and Basu, 1981 Mullen et al., 1985 . Figure 4-22 indicates the nature of scintillation at UHF and L-Band for equatorial regions Basu, 2003 . ji < 11 ,, ( . tliiNUMil ititil illliiL k Figure 4-22 Characteristics of scintillation as observed at Ascension Island in March 2000. The...

Faraday Rotation

Linearly polarized radiowaves may be considered as equivalent to the superposition two equal amplitude circularly polarized waves, but of opposite sense. Faraday rotation occurs in the ionosphere as a result of the fact that two modes (i.e., ordinary and extraordinary waves) propagate in the magneto-ionic medium (i.e., the ionosphere) at different phase velocities. The phase difference between the two modes is proportional to the product of the magnetic field strength and the EC, and inversely...

Ionospheric Models

As in many areas of geophysical study, ionospheric modeling may assume a number of forms ranging from the purely theoretical to the totally empirical. Approaches may also include a combination of these forms, although empirical models dominate the field. Recent developments include allowance for adaptivity within the models to accommodate exploitation in the near-real-time environment for special applications. While physical or theoretical principles are the inspiration for a number of models,...

Definition Of Space Weather

What is space weather The US Department of Defense, in its implementation plan OSD, 2000 , indicates, space weather refers to adverse conditions on the sun, the solar wind, and in the earth's magnetosphere, the ionosphere, and the thermosphere. Indeed this definition portrays those aspects of space weather that are generally of most concern, namely the more pathological elements. But space weather, and ionospheric weather, in particular, can be turbulent or benign. All aspects of space weather...

The Ionosphere 31 Introduction

The ionosphere poses an interesting challenge for many radio systems that make use of signal transmission through all or some portion of the medium. Being a magnetoionic medium imbedded in a background neutral atmosphere, it exhibits very interesting refractive properties, including anisotropy, dispersion and dissipation. The laminar ionosphere introduces an array of effects, which are related to the ionospheric component of radio refractivity. These include ray path bending, phase path...