Ionospheric Alfvén resonator observed at low‐latitude ground station, Muroto

The ionospheric Alfven resonator (IAR) is found in a dynamic power spectrum of the geomagnetic field variations as spectral resonance structures in the frequency range of 0.1–10 Hz. To date, observations of IAR at low latitude have only been made by a few studies employing a single ground observatory and are not sufficient enough to reveal its general characteristics. We analyze data measured with an induction magnetometer installed at Muroto, Japan (24.40° geomagnetic latitude) for the period from 28 December 2013 to 13 August 2016. A statistical analysis reveals that the occurrence probability of the low-latitude IAR is (1) dominant during nighttime with a gradual increase from dusk to midnight and a broad maximum at 00–05 LT followed by a sudden decrease at dawn, (2) slightly higher during May through September, and (3) independent of the Kp index for Kp ≤ 5. We also find that (4) the frequency separation between the harmonics (Δf) of the low-latitude IAR is 0.1–0.5 Hz with a peak at 0.2–0.275 Hz. These observational results are compared with the model calculation results along with previous studies about possible energy sources. It is found that the global thunderstorm activity is a likely source for IAR at Muroto; that is, it produces electromagnetic disturbances that are converted into the Alfven waves and that are then trapped in the ionospheric cavity bounded by the conductive E layer and a steep gradient of Alfven velocity above the F2 layer to form the resonant Alfven waves.

[1]  T. Tsuda,et al.  Seasonal Variation of Solar Atmospheric Tides at Meteor Heights , 1983 .

[2]  L. Baddeley,et al.  Modeling the high‐latitude ground response to the excitation of the ionospheric MHD modes by atmospheric electric discharge , 2016 .

[3]  I. J. Rae,et al.  Effects of substorm dynamics on magnetic signatures of the ionospheric Alfvén resonator , 2010 .

[4]  M. Hayakawa,et al.  Excitation of the ionospheric resonance cavity by neutral winds at middle latitudes , 2004 .

[5]  J. Kangas,et al.  First evidence at high latitudes for the ionospheric Alfvén resonator , 1999 .

[6]  E. Ermakova,et al.  Modeling diurnal variations of the IAR parameters , 2016, Acta Geodaetica et Geophysica.

[7]  A. Nickolaenko,et al.  Parameters of global thunderstorm activity deduced from the long-term Schumann resonance records , 1998 .

[8]  S. Franke,et al.  Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70° N, modelled tides (GSWM, CMAM) , 2002 .

[9]  W. Wan,et al.  Seasonal behavior of meteor radar winds over Wuhan , 2005 .

[10]  Y. Haruta,et al.  Characterization and demonstration results of a SQUID magnetometer system developed for geomagnetic field measurements , 2017 .

[11]  Vassilis Angelopoulos,et al.  Spectral properties of the ionospheric Alfvén resonator observed at a low-latitude station (L = 1.3) , 2002 .

[12]  S. V. Polyakov,et al.  The ionospheric Alfv/'en resonator , 1990 .

[13]  S. V. Poliakov,et al.  The ionospheric Alfven resonator , 1981 .

[14]  Robert L. Lysak,et al.  Feedback instability of the ionospheric resonant cavity , 1991 .

[15]  Vladimir Truhlik,et al.  The International Reference Ionosphere 2012 – a model of international collaboration , 2014 .

[16]  C. Price.  GLOBAL THUNDERSTORM ACTIVITY , 2006 .

[17]  R. Nakamura,et al.  The origin of spectral resonance structures of the ionospheric Alfvén resonator. Single high‐altitude reflection or resonant cavity excitation? , 2014 .

[18]  A. A. Ostapenko,et al.  Comprehensive Morphology of The Spectral Resonance Structure of The Electromagnetic Background Noise In The Range of 0.1-4 Hz At L=5.2 , 2003 .

[19]  E. Ermakova,et al.  Magnetic-inclination effects in the spectral resonance structure of the ionospheric Alfvén resonator , 2009 .

[20]  K. Shiokawa,et al.  ULF impulsive magnetic response at mid-latitudes to lightning activity , 2011 .

[21]  V. Y. Trakhtengerts,et al.  Fine structure in ionospheric Alfvén resonator spectra observed at low latitude (L = 1.3) , 2004 .

[22]  H. Freudenreich,et al.  Detection of ionospheric Alfvén resonator signatures in the equatorial ionosphere , 2012 .

[23]  V. Pilipenko,et al.  IAR signatures in the ionosphere: Modeling and observations at the Chibis-M microsatellite , 2017 .

[24]  M. Hayakawa,et al.  Ionospheric Alfvén resonator excitation due to nearby thunderstorms , 2006 .

[25]  K. Hocke,et al.  Diurnal and semidiurnal tide in the upper middle atmosphere during the first year of simultaneous MF radar observations in northern and southern Japan (45°N and 31°N) , 1999 .

[26]  V. Trakhtengerts,et al.  Experimental studies of the spectral resonance structure of the atmospheric electromagnetic noise background within the range of short-period geomagnetic pulsations , 1989 .

[27]  Masashi Hayakawa,et al.  Ionospheric Alfven resonance at middle latitudes: results of observations at Kamchatka , 2004 .

[28]  Brian Hamilton,et al.  International Geomagnetic Reference Field: the 12th generation , 2015, Earth, Planets and Space.

[29]  Bodo W. Reinisch,et al.  International Reference Ionosphere 2000 , 2001 .

[30]  V. Surkov,et al.  Spatial structure of the electromagnetic field inside the ionospheric Alfvén resonator excited by atmospheric lightning activity , 2012 .

[31]  S. Polyakov.  Ionospheric Alfven resonator , 1981 .

[32]  A. Potapov,et al.  Emissions of ionospheric Alfvén resonator and ionospheric conditions , 2014 .

[33]  A. Nickolaenko,et al.  Variations in global thunderstorm activity inferred from the OTD records , 2006 .

[34]  V. Pilipenko,et al.  Electric field signatures of the IAR and Schumann resonance in the upper ionosphere detected by Chibis-M microsatellite , 2014 .