An empirical model of the quiet daily geomagnetic field variation

[1] An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp ≤ 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity.

[1]  K. Yumoto,et al.  Long-term behavior of annual and semi-annual Sq variations , 2012, Earth, Planets and Space.

[2]  M. G. Cardinal,et al.  Reexamination of the Sq‐EEJ relationship based on extended magnetometer networks in the east Asian region , 2010 .

[3]  Tsutomu Nagatsuma,et al.  Lunar‐dependent equatorial ionospheric electrodynamic effects during sudden stratospheric warmings , 2010 .

[4]  M. G. Cardinal,et al.  Equivalent current systems for the annual and semiannual Sq variations observed along the 210°MM CPMN stations , 2009 .

[5]  J. Liu,et al.  Empirical models of Total Electron Content based on functional fitting over Taiwan during geomagnetic quiet condition , 2009 .

[6]  B. Damtie,et al.  A new index to monitor temporal and long-term variations of the equatorial electrojet by MAGDAS/CPMN real-time data: EE-Index , 2008 .

[7]  Keiko Kawano-Sasaki,et al.  A study on three-dimensional structures of the ionospheric dynamo currents induced by the neutral winds simulated by the Kyushu-GCM , 2008 .

[8]  R. Stening.  The shape of the Sq current system , 2008 .

[9]  Libo Liu,et al.  Solar activity variations of nighttime ionospheric peak electron density , 2006 .

[10]  I. Usoskin,et al.  Long-Term Modulation of the Cosmic Ray Fluctuation Spectrum: Spacecraft Measurements , 2006 .

[11]  A. Chulliat,et al.  On the seasonal asymmetry of the diurnal and semidiurnal geomagnetic variations , 2005 .

[12]  A. Chulliat,et al.  On the semiannual and annual variations of geomagnetic activity and components , 2004 .

[13]  M. Takeda.  The correlation between the variation in ionospheric conductivity and that of the geomagnetic Sq field , 2002 .

[14]  M. Takeda.  Features of global geomagnetic Sq field from 1980 to 1990 , 2002 .

[15]  Kiyohumi Yumoto,et al.  Characteristics of Pi 2 magnetic pulsations observed at the CPMN stations: A review of the STEP results , 2001 .

[16]  M. Takeda.  Time variation of global geomagnetic Sq field in 1964 and 1980 , 1999 .

[17]  M. Acuna,et al.  DC polarization electric field, current density, and plasma density measurements in the daytime equatorial electrojet , 1997 .

[18]  J. Bremer,et al.  Solar cycle dependence and long-term trends in the wind field of the mesosphere/lower thermosphere , 1997 .

[19]  S. Miyahara,et al.  Variation of Sq Induced by Atmospheric Tides Simulated by a Middle Atmosphere General Circulation Model. , 1997 .

[20]  Kiyohumi Yumoto,et al.  The step 210° Magnetic meridian network Project , 1996 .

[21]  R. Stening.  Variations in the strength of the Sq current system , 1995 .

[22]  N. Fukushima.  Some topics and historical episodes in geomagnetism and aeronomy , 1994 .

[23]  P. Richards,et al.  EUVAC: A solar EUV Flux Model for aeronomic calculations , 1994 .

[24]  S. Alex,et al.  Seasonal Variations of Geomagnetic D, H and Z Fields at Low Latitudes , 1994 .

[25]  W. Campbell,et al.  External Sq currents in the India-Siberia region , 1993 .

[26]  G. J. Bailey,et al.  Ionospheric evidence for a nonlinear relationship between the solar e.u.v. and 10.7 cm fluxes during an intense solar cycle , 1993 .

[27]  W. Campbell,et al.  Quiet Geomagnetic Field Representation for All Days and Latitudes , 1992 .

[28]  W. Campbell.  Differences in geomagnetic Sq field representations due to variations in spherical harmonic analysis techniques , 1990 .

[29]  W. Campbell.  An introduction to quiet daily geomagnetic fields , 1989 .

[30]  Wenlan Xu.  Polar regionSq , 1989 .

[31]  T. Tsuda,et al.  Asymmetries in mesospheric tidal structure , 1989 .

[32]  R. Stening.  A diurnal modulation of the lunar tide in the upper atmosphere , 1989 .

[33]  W. Campbell,et al.  Global quiet day field variation model WDCA/SQ1 , 1989 .

[34]  T. Tsuda,et al.  A comparative study of mesospheric solar tides observed at Adelaide and Kyoto , 1988 .

[35]  W. Campbell,et al.  Correction to “Quiet ionospheric currents of the northern hemisphere derived from geomagnetic field records” , 1986 .

[36]  T. Araki,et al.  Simulation of ionospheric currents and geomagnetic field variations of Sq for different solar activity , 1986 .

[37]  W. Campbell,et al.  Quiet ionospheric currents of the southern hemisphere derived from geomagnetic records , 1985 .

[38]  T. Araki,et al.  Electric conductivity of the ionosphere and nocturnal currents , 1985 .

[39]  F. Hibberd.  The geomagnetic Sqvariation—annual, semi-annual and solar cycle variations and ring current effects , 1985 .

[40]  B. Briggs.  The variability of ionospheric dynamo currents , 1984 .

[41]  S. Matsushita.  Cautions for the estimation of equivalent current systems from geomagnetic data , 1983 .

[42]  S. Matsushita,et al.  Equivalent ionospheric current systems representing solar daily variations of the polar geomagnetic field , 1982 .

[43]  W. Campbell,et al.  Sq currents: A comparison of quiet and active year behavior , 1982 .

[44]  W. Campbell.  Annual and semiannual changes of the quiet daily variations (Sq) in the geomagnetic field at North American locations , 1982 .

[45]  W. Campbell.  Annual and semiannual variations of the geomagnetic field at equatorial locations. , 1981 .

[46]  D. Möhlmann,et al.  Large-scale electric fields and currents and related geomagnetic variations in the quiet plasmasphere , 1980 .

[47]  J. D. Tarpley,et al.  On the production mechanism of electric currents and fields in the ionosphere , 1976 .

[48]  S. Matsushita.  IMF polarity effects on the Sq current focus location , 1975 .

[49]  T. Yabuzaki,et al.  Rocket measurement of Sq ionospheric currents over Kagoshima, Japan , 1974 .

[50]  S. Malin.  Worldwide distribution of geomagnetic tides , 1973, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[51]  W. Campbell,et al.  Lunar semidiurnal variations of the geomagnetic field determined from the 2.5-min data scalings , 1972 .

[52]  R. P. Kane.  Relationship between Day to Day Variability of Sq and Interplanetary Plasma Parameters , 1971 .

[53]  N. Trivedi,et al.  LUNI--SOLAR TIDES IN H AT STATIONS WITHIN THE EQUATORIAL ELECTROJET. , 1970 .

[54]  S. Matsushita.  Dynamo currents, winds, and electric fields , 1969 .

[55]  M. Sugiura,et al.  Lunar phase numbers nu and nu' for years 1850 to 2050 , 1966 .

[56]  D. Rao,et al.  Solar cycle and annual variations of Sq(H) at Alibag , 1966 .

[57]  Sadami Matsushita,et al.  On the Geomagnetic Solar Quiet Daily Variation Field , 1965 .

[58]  H. Takeuchi,et al.  Electromagnetic induction within the Earth , 1963 .

[59]  N. S. Alexander,et al.  Variations in the geomagnetic field at Ibadan, Nigeria—II Lunar and luni-solar variations in H and Z , 1959 .

[60]  W. M. W..  The Earth's Magnetism , 1936, Nature.

[61]  Wallace H. Campbell,et al.  Introduction to Geomagnetic Fields: Applications , 2003 .

[62]  D. Bilitza.  The importance of EUV indices for the international reference ionosphere , 2000 .

[63]  W. H. Campbell.  The regular geomagnetic-field variations during quiet solar conditions. , 1989 .

[64]  S. Matsushita,et al.  Seasonal variations of L equivalent current systems , 1984 .

[65]  W. Campbell.  Annual and semiannual variations of the lunar semidiurnal geomagnetic field components at North American locations. , 1980 .

[66]  K. Iyer,et al.  Quiet day variation of geomagnetic H-field at low latitudes. , 1976 .

[67]  A. Suzuki.  A New Analysis of the Geomagnetic Sq Field , 1973 .

[68]  R. Rastogi.  LUNAR TIDAL OSCILLATIONS IN H AT HUANCAYO DURING IGY/IGC. , 1968 .

[69]  A. T. Price.  II-3 - Electromagnetic Induction within the Earth , 1967 .

[70]  A. Yacob,et al.  Solar control of the amplitude and phase of the yearly mean Sq(H) at Alibag for the period 1905 to 1960 , 1965 .

[71]  M. Geller.  Lunar Tide in the Atmosphere , 1940, Nature.

[72]  William Ellis,et al.  XV. On the relation between the diurnal range of magnetic declination and horizontal force, as observed at the Royal Observatory, Greenwich, during the years 1841 to 1877, and the period of solar spot frequency , 1880, Philosophical Transactions of the Royal Society of London.