DOCSLIB.ORG

Detection of Ionospheric Perturbations Associated with Japanese Earthquakes on the Basis of Reception of LF Transmitter Signals on the Satellite DEMETER

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Detection of Ionospheric Perturbations Associated with Japanese Earthquakes on the Basis of Reception of LF Transmitter Signals on the Satellite DEMETER Nat. Hazards Earth Syst. Sci., 8, 135–141, 2008 www.nat-hazards-earth-syst-sci.net/8/135/2008/ Natural Hazards © Author(s) 2008. This work is licensed and Earth under a Creative Commons License. System Sciences Detection of ionospheric perturbations associated with Japanese earthquakes on the basis of reception of LF transmitter signals on the satellite DEMETER F. Muto1, M. Yoshida1, T. Horie1, M. Hayakawa1, M. Parrot2, and O. A. Molchanov3 1Department of Electronic Engineering and Research Station on Seismo Electromagnetics, University of Electro-Communications, Chofu Tokyo, Japan 2LPCE/CNRS, Orleans, France 3Institute of Physics of the Earth, Moscow, Russia Received: 22 November 2007 – Revised: 22 January 2008 – Accepted: 22 January 2008 – Published: 26 February 2008 Abstract. There have been recently reported a lot of elec- 1 Introduction tromagnetic phenomena associated with earthquakes (EQs). Among these, the ground-based reception of subionospheric EQ precursory signature is recently known to appear not waves from VLF/LF transmitters, is recognized as a promis- only in the lithosphere, but also in the atmosphere and iono- ing tool to investigate the ionospheric perturbations associ- sphere (e.g., Hayakawa, 1999; Hayakawa and Molchanov, ated with EQs. This paper deals with the corresponding 2002). This means that EQs can excite atmospheric and whistler-mode signals in the upper ionosphere from those ionospheric perturbations by direct coupling, which leads VLF/LF transmitters, which is the counterpart of subiono- us to use a new terminology of “Lithosphere-Atmosphere- spheric signals. The whistler-mode VLF/LF transmitter sig- Ionosphere Coupling”. The ionosphere seems to be disturbed nals are detected on board the French satellite, DEME- in different height regions. For example, recent works by TER launched on 29 June 2004. We have chosen several Liu et al. (2000, 2006) have suggested in the statistical sense large Japanese EQs including the Miyagi-oki EQ (16 August that the ionospheric F layer is apparently disturbed during 2005; M=7.2, depth=36 km), and the target transmitter is a EQs. Also, we can cite a recent event study by Hobara and Japanese LF transmitter (JJY) whose transmitter frequency Parrot (2005). While, the lower ionosphere (D/E layer) is is 40 kHz. Due to large longitudinal separation of each satel- found already to be extremely sensitive to seismicity. This lite orbit (2500 km), we have to adopt a statistical analysis was confirmed by means of subionospheric VLF/LF prop- over a rather long period (such as 3 weeks or one month) to agation anomalies (Molchanov and Hayakawa, 1998) since have reliable data set. By analyzing the spatial distribution of the pioneering discovery of clear seismo-ionospheric pertur- JJY signal intensity (in the form of signal to noise ratio SNR) bations for the Kobe EQ (Hayakawa et al., 1996). Because during a period of 4 months including the Miyagi-oki EQ, we VLF/LF radio waves are known to propagate in the Earth- have found significant changes in the intensity; generally the ionosphere waveguide, any change in the lower ionosphere SNR is significantly depleted before the EQ, which is con- may result in significant changes in the VLF signal received sidered to be a precursory ionospheric signature of the EQ. at a station (Molchanov and Hayakawa, 1998; Molchanov This abnormal effect is reasonably explained in terms of ei- et al., 2001; Hayakawa, 2004; Hayakawa et al., 2004; Bi- ther (1) enhanced absorption of whistler-mode LF signals in agi et al., 2007). Recently, statistical analyses on the cor- the lower ionosphere due to the lowering of the lower iono- relation between the lower ionospheric perturbation as de- sphere, or (2) nonlinear wave-wave scattering. Finally, this tected by subionospheric VLF/LF signals and EQs, have analysis suggests an important role of satellite observation in been performed by Rozhnoi et al. (2004) and Maekawa et the study of lithosphere-atmosphere-ionosphere coupling. al. (2006), who have concluded that the lower ionosphere is definitely perturbed for the shallow EQs with magnitude greater than 6.0. Of course, it is not well understood at the moment how the ionosphere is perturbed due to the seismic- Correspondence to: M. Hayakawa ity, though there have been proposed a few possible mech- ([email protected]) anisms on the lithosphere-atmosphere-ionosphere coupling Published by Copernicus Publications on behalf of the European Geosciences Union. 136 F. Muto et al.: Satellite LF detection of seismo-ionospheric perturbations DEMETER 125 130 135 140 145 150 700 km depth km 45 0 20 40 60 80 100 45 Whistler mode Field Line 80 km Ionosphere Perturbation 40 8/16 8/24 JJY 8/30 VLF Radio Waves 8/7 7/23 6/19 35 Geographic Latitude [deg] VLF Transmitter 7/9 7/27 Epicenter VLF Receiver km Fig. 1. The model of VLF/LF wave propagation, in which there 30 30 are two modes of propagation: Earth-ionosphere waveguide mode M:over 5.5 0 500 and whistler mode in the ionospheric plasma. The mechanism of 125 130 135 140 145 150 Lithosphere-Atmosphere-Ionosphere Coupling is plotted. Geographic Longitude [deg] Fig. 2. Relative location of the LF transmitter in Fukushima, JJY and the epicenters of the target EQs including Miyagi-oki EQ. The size of an EQ is proportional to its magnitude. (see Molchanov et al., 2001; Hayakawa, 2004; Sorokin et al., 2005; Molchanov and Hayakawa, 2008). 2 Analyzed EQs As is shown in Fig. 1, a VLF/LF transmitter emits elec- Figure 2 illustrates the relative location of our LF transmitter ◦ tromagnetic waves at a particular frequency mainly in the in Fukushima prefecture (geographic coordinates: 37 22’N, ◦ subionospheric waveguide, which are used to infer the 140 51’E), and the epicenters of our target EQs around seismo-ionospheric perturbations as mentioned above (e.g., Japan. The JJY transmission frequency is 40 kHz, and the Hayakawa et al., 1996; Molchanov and Hayakawa, 1998). transmitter power is 50 kW. These target EQs are summa- While, another part of VLF/LF transmitter signals is known rized in Table 1, in which we have chosen several EQs dur- to penetrate upward into the ionosphere/magnetosphere in ing a period from 1 June 2005 to 30 September 2005. The whistler mode (Hayakawa, 1995). This kind of whistler- selection criteria are as follows; (1) the magnitude of these mode VLF transmitter signal is also expected to provide EQs is greater than 5.5, and (2) the depth is less than 100 km. us with further information on the seismo-ionospheric per- Molchanov and Hayakawa (1998) indicated that only shal- turbation because of their penetration through this region. low EQs can influence the lower ionosphere, which is the In fact, Molchanov et al. (2006) have recently found sig- reason why we adopt the latter condition The former crite- nificant seismo-ionospheric effects associated with a huge rion has been recently confirmed by statistical analyses by Sumatra EQ in December, 2004 by using the VLF data ob- Rozhnoi et al. (2004) and Maekawa et al. (2006). As is seen served on board the French satellite, DEMETER. And, this in Table 1, we have a large EQ, named Miyagi-oki EQ hap- satellite finding is found to be in good consistence with our pened on 16 August 2005 with magnitude of 7.2 and with ground-based VLF observation for the same EQ by Horie depth of 36 km. This EQ will be the main target of our anal- et al. (2007a, b). This paper is a further extension of the ysis. paper by Molchanov et al. (2006), which deals with further event studies for Japanese EQs by using the same DEME- TER VLF/LF wave data. The satellite, DEMETER was 3 LF wave data on DEMETER and analysis methods launched on 29 June 2004, and it is working well with the aim of studying seismo-electromagnetic effects (Parrot et al., We follow the analysis method by Molchanov et al. (2006). 2006). In this paper we have chosen several large Japanese Following Molchanov et al. (2006), we compute the signal to EQs including the Miyagi-oki EQ (16 August 2005; M=7.2, noise ratio (SNR) that is defined as follows. depth=36 km), and the target transmitter is a Japanese LF transmitter (JJY) whose transmitter frequency is 40 kHz and 2A(f ) SNR = 0 . (1) which is located in Fukushima prefecture (Hayakawa, 2004). A(f−) + A(f+) Nat. Hazards Earth Syst. Sci., 8, 135–141, 2008 www.nat-hazards-earth-syst-sci.net/8/135/2008/ F. Muto et al.: Satellite LF detection of seismo-ionospheric perturbations 137 Table 1. Details of the EQs selected. Data Lat. [deg] Long. [deg] Area Depth [km] M 2005.6.19 35.61 140.48 Chiba 48 5.7 2005.7.9 33.42 140.82 coast of southern Chiba 55 5.8 2005.7.23 35.50 139.98 Tokyo Bay 61 6.1 2005.7.27 33.26 142.32 coast of southeastern Chiba 33 5.5 2005.8.7 36.33 141.37 coast of Ibaraki 39 5.5 2005.8.16 38.28 142.04 coast of Miyagi 36 7.2 2005.8.24 38.56 142.99 coast of Miyagi 10 6.1 2005.8.30 38.48 143.18 coast of Miyagi 21 6.1 where A(f0) is the amplitude spectrum density in the 0.5 frequency band including the transmitter (JJY) frequency (40 kHz), and A(f±) are the background noise value out- 0.4 side the signal band. On the satellite DEMETER we ob- serve the electromagnetic waves (electric field) in two dif- 0.3 ferent frequency bands: VLF range (below 20 kHz) and higher frequency range (above 20 kHz).
Load more

Recommended publications
  • QUICK REFERENCE GUIDE Latitude, Longitude and Associated Metadata
    QUICK REFERENCE GUIDE Latitude, Longitude and Associated Metadata The Property Profile Form (PPF) requests the property name, address, city, state and zip. From these address fields, ACRES interfaces with Google Maps and extracts the latitude and longitude (lat/long) for the property location. ACRES sets the remaining property geographic information to default values. The data (known collectively as “metadata”) are required by EPA Data Standards. Should an ACRES user need to be update the metadata, the Edit Fields link on the PPF provides the ability to change the information. Before the metadata were populated by ACRES, the data were entered manually. There may still be the need to do so, for example some properties do not have a specific street address (e.g. a rural property located on a state highway) or an ACRES user may have an exact lat/long that is to be used. This Quick Reference Guide covers how to find latitude and longitude, define the metadata, fill out the associated fields in a Property Work Package, and convert latitude and longitude to decimal degree format. This explains how the metadata were determined prior to September 2011 (when the Google Maps interface was added to ACRES). Definitions Below are definitions of the six data elements for latitude and longitude data that are collected in a Property Work Package. The definitions below are based on text from the EPA Data Standard. Latitude: Is the measure of the angular distance on a meridian north or south of the equator. Latitudinal lines run horizontal around the earth in parallel concentric lines from the equator to each of the poles.
    [Show full text]
  • A Stability Analysis of Divergence Damping on a Latitude–Longitude Grid
    2976 MONTHLY WEATHER REVIEW VOLUME 139 A Stability Analysis of Divergence Damping on a Latitude–Longitude Grid JARED P. WHITEHEAD Department of Mathematics, University of Michigan, Ann Arbor, Ann Arbor, Michigan CHRISTIANE JABLONOWSKI AND RICHARD B. ROOD Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Ann Arbor, Michigan PETER H. LAURITZEN Climate and Global Dynamics Division, National Center for Atmospheric Research,* Boulder, Colorado (Manuscript received 24 August 2010, in final form 25 March 2011) ABSTRACT The dynamical core of an atmospheric general circulation model is engineered to satisfy a delicate balance between numerical stability, computational cost, and an accurate representation of the equations of motion. It generally contains either explicitly added or inherent numerical diffusion mechanisms to control the buildup of energy or enstrophy at the smallest scales. The diffusion fosters computational stability and is sometimes also viewed as a substitute for unresolved subgrid-scale processes. A particular form of explicitly added diffusion is horizontal divergence damping. In this paper a von Neumann stability analysis of horizontal divergence damping on a latitude–longitude grid is performed. Stability restrictions are derived for the damping coefficients of both second- and fourth- order divergence damping. The accuracy of the theoretical analysis is verified through the use of idealized dynamical core test cases that include the simulation of gravity waves and a baroclinic wave. The tests are applied to the finite-volume dynamical core of NCAR’s Community Atmosphere Model version 5 (CAM5). Investigation of the amplification factor for the divergence damping mechanisms explains how small-scale meridional waves found in a baroclinic wave test case are not eliminated by the damping.
    [Show full text]
  • RAMP: a Computer System for Mapping Regional Areas
    RAMP: a computer system for mapping regional areas Bradley B. Nickey PACIFIC SOUTHWEST Forest and Range Experiment Station FOREST SERVICE lJ S DEPARTMENT OF AGRICULTURE P.O. BOX 245, BERKELEY, CALIFORNIA 94701 USDA FOREST SERVICE GENERAL TECHNICAL REPORT PSW-12 11975 CONTENTS Page Introduction ........................................... 1 Individual Fire Reports ................................... 1 RAMP ................................................ 2 Digitization Requirements ................................. 2 Accuracy .............................................. 2 Computer Software ...................................... 2 Computer Operations .................................... 4 Converting Coordinates ................................ 4 Aligning Coordinates .................................. 4 Mapping Sections ..................................... 6 Application ............................................ 8 Literature Cited ......................................... 9 Nickey, Bradley B. 1975. RAMP: a computer system for mapping regional areas. USDA Forest Serv. Gen. Tech. Rep. PSW-12, 9 p., illus. Pacific Southwest Forest and Range Exp. Stn., Berkeley, Calif. Until 1972, the U.S. Forest Service's Individual Fire Reports recorded locations by the section-township-range system..These earlier fire reports, therefore, lacked congruent locations. RAMP (Regional Area Mapping Pro- cedure) was designed to make the reports more useful for quantitative analysis. This computer-based technique converts locations expressed in section-township-range
    [Show full text]
  • Five Years of VLF Worldwide Comparison of Atomic Frequency Standards
    RADIO SCIENCE, Vol. 2 (New Series), No. 6, June 1967 Five Years of VLF Worldwide Comparison of Atomic Frequency Standards B. E. Blair,' E. 1. Crow,2 and A. H. Morgan (Received January 19, 1967) The VLF radio broadcasts of GBR(16.0 kHz), NBA(18.0 or 24.0 kHz), and NSS(21.4 kHz) have enabled worldwide comparisons of atomic frequency standards to parts in 1O'O when received over varied paths and at distances up to 9000 or more kilometers. This paper summarizes a statistical analysis of such comparison data from laboratories in England, France, Switzerland, Sweden, Russia, Japan, Canada, and the United States during the 5-year period 1961-1965. The basic data are dif- ferences in 24-hr average frequencies between the local atomic standard and the received VLF radio signal expressed as parts in 10"'. The analysis of the more recent data finds the receiving laboratory standard deviations, &, and the transmission standard deviation, ?, to be a few parts in 10". Averag- ing frequencies over an increasing number of days has the effect of reducing iUi and ? to some extent. The variation of the & with propagation distance is studied. The VLF-LF long-term mean differences between standards are compared with the recent portable clock tests, and they agree to parts in IO". 1. Introduction points via satellites (Steele, Markowitz, and Lidback, 1964; Markowitz, Lidback, Uyeda, and Muramatsu, Six years ago in London, the XIIIth General Assem- 1966); improvements in the transmission of VLF and bly of URSI adopted a resolution (No. 2) which strongly LF radio signals (Milton, Fey, and Morgan, 1962; recommended continuous very-low-frequency (VLF) Barnes, Andrews, and Allan, 1965; Bonanomi, 1966; and low-frequency (LF) transmission monitoring US.
    [Show full text]
  • Observed Time Difference of Arrival (OTDOA) Positioning in 3GPP LTE
    Observed Time Difference Of Arrival (OTDOA) Positioning in 3GPP LTE by Sven Fischer June 6, 2014 © 2014 Qualcomm Technologies, Inc. Contents 1 Scope ................................................................................................................ 7 2 References ....................................................................................................... 8 3 Definitions and Abbreviations ........................................................................ 9 3.1 Definitions .................................................................................................................... 9 3.2 Abbreviations .............................................................................................................. 10 4 Multilateration in OTDOA Positioning ......................................................... 12 4.1 Introduction ................................................................................................................. 12 4.2 Reference Signal Time Difference Measurement (RSTD) ......................................... 13 4.2.1 Definition ......................................................................................................... 13 4.2.2 RSTD Measurement Report Mapping ............................................................. 13 4.3 Basic OTDOA Navigation Equations ......................................................................... 13 5 Positioning Reference Signals (PRS) .......................................................... 15 5.1 Overview ....................................................................................................................
    [Show full text]
  • Time Signal Stations 1By Michael A
    122 Time Signal Stations 1By Michael A. Lombardi I occasionally talk to people who can’t believe that some radio stations exist solely to transmit accurate time. While they wouldn’t poke fun at the Weather Channel or even a radio station that plays nothing but Garth Brooks records (imagine that), people often make jokes about time signal stations. They’ll ask “Doesn’t the programming get a little boring?” or “How does the announcer stay awake?” There have even been parodies of time signal stations. A recent Internet spoof of WWV contained zingers like “we’ll be back with the time on WWV in just a minute, but first, here’s another minute”. An episode of the animated Power Puff Girls joined in the fun with a skit featuring a TV announcer named Sonny Dial who does promos for upcoming time announcements -- “Welcome to the Time Channel where we give you up-to- the-minute time, twenty-four hours a day. Up next, the current time!” Of course, after the laughter dies down, we all realize the importance of keeping accurate time. We live in the era of Internet FAQs [frequently asked questions], but the most frequently asked question in the real world is still “What time is it?” You might be surprised to learn that time signal stations have been answering this question for more than 100 years, making the transmission of time one of radio’s first applications, and still one of the most important. Today, you can buy inexpensive radio controlled clocks that never need to be set, and some of us wear them on our wrists.
    [Show full text]
  • Latitude and Longitude
    Latitude and Longitude Finding your location throughout the world! What is Latitude? • Latitude is defined as a measurement of distance in degrees north and south of the equator • The word latitude is derived from the Latin word, “latus”, meaning “wide.” What is Latitude • There are 90 degrees of latitude from the equator to each of the poles, north and south. • Latitude lines are parallel, that is they are the same distance apart • These lines are sometimes refered to as parallels. The Equator • The equator is the longest of all lines of latitude • It divides the earth in half and is measured as 0° (Zero degrees). North and South Latitudes • Positions on latitude lines above the equator are called “north” and are in the northern hemisphere. • Positions on latitude lines below the equator are called “south” and are in the southern hemisphere. Let’s take a quiz Pull out your white boards Lines of latitude are ______________Parallel to the equator There are __________90 degrees of latitude north and south of the equator. The equator is ___________0 degrees. Another name for latitude lines is ______________.Parallels The equator divides the earth into ___________2 equal parts. Great Job!!! Lets Continue! What is Longitude? • Longitude is defined as measurement of distance in degrees east or west of the prime meridian. • The word longitude is derived from the Latin word, “longus”, meaning “length.” What is Longitude? • The Prime Meridian, as do all other lines of longitude, pass through the north and south pole. • They make the earth look like a peeled orange. The Prime Meridian • The Prime meridian divides the earth in half too.
    [Show full text]
  • STANDARD FREQUENCIES and TIME SIGNALS (Question ITU-R 106/7) (1992-1994-1995) Rec
    Rec. ITU-R TF.768-2 1 SYSTEMS FOR DISSEMINATION AND COMPARISON RECOMMENDATION ITU-R TF.768-2 STANDARD FREQUENCIES AND TIME SIGNALS (Question ITU-R 106/7) (1992-1994-1995) Rec. ITU-R TF.768-2 The ITU Radiocommunication Assembly, considering a) the continuing need in all parts of the world for readily available standard frequency and time reference signals that are internationally coordinated; b) the advantages offered by radio broadcasts of standard time and frequency signals in terms of wide coverage, ease and reliability of reception, achievable level of accuracy as received, and the wide availability of relatively inexpensive receiving equipment; c) that Article 33 of the Radio Regulations (RR) is considering the coordination of the establishment and operation of services of standard-frequency and time-signal dissemination on a worldwide basis; d) that a number of stations are now regularly emitting standard frequencies and time signals in the bands allocated by this Conference and that additional stations provide similar services using other frequency bands; e) that these services operate in accordance with Recommendation ITU-R TF.460 which establishes the internationally coordinated UTC time system; f) that other broadcasts exist which, although designed primarily for other functions such as navigation or communications, emit highly stabilized carrier frequencies and/or precise time signals that can be very useful in time and frequency applications, recommends 1 that, for applications requiring stable and accurate time and frequency reference signals that are traceable to the internationally coordinated UTC system, serious consideration be given to the use of one or more of the broadcast services listed and described in Annex 1; 2 that administrations responsible for the various broadcast services included in Annex 2 make every effort to update the information given whenever changes occur.
    [Show full text]
  • What Time I T
    Does Anybody Really What Time It Is? 24/7/365, Here's How Time Got On Your Best Side By Michael A. Lombardi ccasionally I'll talk to people who known to most radio buffs. He used a can't believe that some radio sta- spark-gap transmitter to successfully 0tions exist solely to transmit accu- send radio signals over a distance of more rate time. While they wouldn't poke fun than one mile in 1895. By 1899 he had at the Weather Channel or even a radio transmitted signals across the English station that plays nothing but Garth Channel, and sent signals across the Brooks records (imagine that), people Atlantic Ocean in 1901. often make jokes about time signal sta- Surprisingly, in the midst of Marconi's tions. They'll ask "Doesn't the program- early work, before any radio stations exist- ming get a little boring?'or "How does ed, or before the public even completely the announcer stay awake?'There have believed his results, a proposal was made even been parodies of time signal sta- to use the new wireless medium to broad- tions. A recent Internet spoof of WWV cast time. In November 1898. an optical containedzingers like "we'll be back with instrument maker and inventor named Sir the time on WWV in just a minute, but Howard Grubb addressed the Royal first, here's another minute." Dublin Society and proposed the concept An episode of the animated Powerpuff of a radio controlled clock. After many Girls joined in the fun with a skit featur- years of working with astronomical obser- ing a TV announcer named Sonnv Dial L, vatories.
    [Show full text]
  • Time and Frequency Users' Manual
    ,>'.)*• r>rJfl HKra mitt* >\ « i If I * I IT I . Ip I * .aference nbs Publi- cations / % ^m \ NBS TECHNICAL NOTE 695 U.S. DEPARTMENT OF COMMERCE/National Bureau of Standards Time and Frequency Users' Manual 100 .U5753 No. 695 1977 NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, a technical (3) basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the Office of Experimental Technology Incentives Program. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essen- tial services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics
    [Show full text]
  • LSI for Radio Clocks
    LSI for Radio Clocks Takayuki Kondo Katsuya Maruyama Tsunao Oike Radio clocks sustain accurate time at all times, as The broadcasting of time information is conducted in they are equipped with functions for receiving low Japan by the National Institute of Information and frequency signals (the standard-time and frequency- Communications Technology, an incorprated signal emission) that carry time information and administrative agency, with the standard frequency automatically correct time and calendars. Products fitted transmitting offices established at two locations including with a radio clock function are on the increase, since the Ohtakado-yama standard frequency station in Fukushima broadcast range of the standard frequency was extended Prefecture (1997) and Hagane-yama standard frequency to cover all Japan in 2001, which resulted in radio clocks station in Saga Prefecture (2001). Each transmitting getting into the limelight. station covers a radius of 1,200km and the two Conventional radio clocks were used as ordinary transmitting stations combined cover almost the entire clocks (table clocks, watches, wall clocks, etc.) but with area of Japan (Figure 2). Further, mutual interference is the recent improvement of LSIs for radio receiver and avoided with different frequencies assigned, 40KHz from antennas combined with a reduction in power Ohtakado-yama station (Fukushima-Pref.) and 60KHz consumption, raised sensitivity and miniaturization, from Hagane-yama station (Saga-Pref.). application of the device in various products is anticipated, such as consumer appliances, mobile devices and home electric appliances. This paper will provide a general summary of the “ML6191”, a real-time clock LSI with an automatic time correction function that is a combination of the RF for the Approx.
    [Show full text]
  • Ark Atwood Year Five Knowledge Organiser Around the World
    Ark Atwood Year Five Knowledge Organiser Around the World Links to Other Units You should already know: Y1 Around the the countries of Europe World natural disasters and why they occur Y3 Natural disasters that civilisations and Empires are of- Y4 Rivers over Time ten formed through conflict Y4 Endangered ani- climate change affects wildlife as well mals as humans Prime Meridian The prime meridian is the imaginary Glossary line that divides Earth into two equal parts: the Eastern Hemisphere and the Western Hemisphere. The prime merid- 1 Continent One of the earth's seven major areas of land (eg Europe, Asia etc) ian is also used as the basis for the 2 Equator The imaginary circle around the earth that is halfway between the North and South Poles world’s time zones. 3 Latitude The distance between the equator and a point north or south on the Earth's surface. This dis- The prime meridian appears on maps tance is measured in degrees. and globes. It is the starting point for 4 Longitude Distance on the Earth's surface east or west of an imaginary line on the globe that goes from the measuring system called longitude. the north pole to the south pole and passes through Greenwich. Longitude is usually measured Longitude is a system of imaginary in degrees. north-south lines called meridians. They connect the North Pole to the 6 Time Zone A region in which all the clocks are set to the same time. The Earth is divided into twenty-four South Pole. time zones.
    [Show full text]