Space weather effects on Communication: Geomagnetic activity and Radio wave absorption in the equato

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Space weather effects on CommunicationGeomagneti
c activity and Radio wave absorption in the
equatorial region

• Victor U Chukwuma
• Department of Physics, Olabisi Onabanjo
  University,
• P. O Box 351, Ago-Iwoye, Nigeria
• E-mail victorchukwuma_at_yahoo.com
• On Sabbatical Leave at Lagos State University
• For all correspondence

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Outline

• Introduction
• Interplanetary and Geomagnetic phenomenon.
• Ionospheric response.
• Storm effects on radio wave propagation

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Introduction

• Space weather refers to the conditions on the Sun
  , the solar wind, magnetosphere, ionosphere and
  the thermosphere that can influence the
  performance and reliability of satellite- and
  ground based technological systems. Central to
  space weather are intense geomagnetic storms.
• This paper presents the results of two
  independent studies that reinforce one another in
  implying that space weather, as manifested in
  intense geomagnetic storms, adversely affect HF
  radio communication. This is due to the fact that
  HF radio communication depends on the
  ionosphere.
• The first part of the paper presents the
  interplanetary origin of an intense storm, the
  geomagnetic and ionospheric response to the
  interplanetary structures
• The second part presents the effect of
  geomagnetic activity on radio wave absorption

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Interplanetary and Geomagnetic Observation data

• These are OMNI hourly averaged definitive
  multi-spacecraft interplanetary parameters data
  and are the proton number density, the solar wind
  flow speed, the interplanetary magnetic field
  component Bz, the plasma beta and the dawn-dusk
  electric field. These data are obtained from
  NSSDCs OMNIWeb Service (http//nssdc.gsfc.nasa.go
  v/omniweb). Hourly values of the low-latitude
  magnetic index, Dst which are derived from
  low-latitude stations and are obtained from the
  National Geophysical Data Centre's SPIDR OMNI IMF
  data (http// spidr.ngdc.noaa.gov).

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Solar wind, IMF Magnetosphere
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Coronal Mass Ejection
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Magnetic reconnection
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Interplanetary and Geomagnetic phenomenon
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Ionospheric data

• The Ionospheric data used in this study consists
  of hourly values of foF2 obtained from some of
  the National Geophysical Data Centre's SPIDR
  ?Space Physics Interactive Data Resource) a
  network of ionosonde stations located in the
  East Asian sector Yakutsk, Wakkanai, Akita,
  Kokubunji, Yamagawa, Okinawa and Manila. These
  stations are listed in Table 1. The present study
  is concerned with variations in foF2 due to the
  geomagnetic storms of July 13-14, 1982. However,
  the F2 region response to geomagnetic storms is
  most conveniently described in terms of D(foF2) ,
  that is the normalized deviations of the critical
  frequency foF2 from the reference (Chukwuma,
  2003b)

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Ionosonde Stations
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Ionospheric response
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Storm effects on radio wave propagation
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Determination of Absorption

• Absorption data for the present study was
  obtained at 4.87 MHz at 1000hrs LT at Lagos
  (3.40oE, 6.55oN) using A3 method The transmitter
  (Radio Cotonou) is located at Cotonou 2.43oE,
  6.35oN.The storm data are obtained from the IUGG
  bulletin published by Institut Fur Geophysik,
  Gottingen, Germany. The absorption of HF radio
  wave for any circuit when the height of
  reflection of the radio wave, as in the case of
  the Cotonou Lagos circuit, is the same for both
  daytime and night time is given as
• The absorption data represents the total
  absorption from
• the F region in which the radio wave is
  reflected a considerable amount of the total
  absorption occurs near the top of the radio wave
  trajectory in the deviating region.
• the E region, where the collisional frequency is
  relatively high, while the refractive index is
  still nearly unity.

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Variations in geomagnetic activity and
ionospheric absorption around all severe
storms.
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Variations in geomagnetic activity and
ionospheric absorption around severe storms with
SSC .
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Summary

• A study of the effect of space weather on HF
  radio communication has been presented. The
  paper consists of the investigation of the
  intense storm of July 13-14, 1982(Dst -325 nT)
  on the one hand and the investigation of the
  effect of geomagnetic storms on equatorial radio
  wave absorption on the other hand. In the first
  part of the study, the structure of the storm of
  July 13-14, 1982(Dst -325 nT) is presented
  using the low-latitude magnetic index, Dst and is
  interpreted using solar wind interplanetary data,
  while the F2 region structure response to the
  geomagnetic storm was studied using foF2 data
  obtained during the storms from a network of
  ionosonde stations. In the second part, the
  effect of geomagnetic storms on equatorial radio
  wave absorption was investigated using severe
  storms (Ap ? 54) and HF absorption data obtained
  on 4.87 MHz at 1000 hours LT at Lagos (3.40oE,
  6.55oN). The results of these independent
  investigations have been found to reinforce one
  another in implying that space weather, as
  manifested in intense geomagnetic storms,
  adversely affect HF radio communication.

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Conclusion

• Earlier investigations of the influence of
  geomagnetic storms on radio wave absorption were
  based on storm selection criterion that lumped
  together weak, moderate, and strong storms
  together, and favouring weak and moderate weak
  storms the selection made it impossible for the
  investigations to detect any change in equatorial
  radio wave absorption following geomagnetic
  storms. The present result obtained using the
  superposed epoch method shows that HF absorption
  in the equatorial ionosphere increases after
  severe geomagnetic activity.