Nighttime D region electron density measurements from ELF‐VLF tweek radio atmospherics recorded at low latitudes

[1] Dispersive atmospherics (tweeks) observed during 2010 simultaneously at two low-latitude stations, Allahabad (geomagnetic latitude, 16.05°N) and Nainital (geomagnetic latitude, 20.48°N), have been used to estimate the nighttime D region electron density at the ionospheric reflection height under the local nighttime propagation (21:00–02:00 LT or 15:30–20:30 UT). The analysis of simultaneously recorded tweeks at both the stations on five international quiet days during one month each from summer (June), winter (January), and equinox (March) seasons shows that the D region electron density varies 21.5–24.5 cm−3 over the ionospheric reflection height of 85–95 km. The average values of Wait lower ionospheric parameters: ionospheric reference height h′ and sharpness factor β are almost same during winter (85.9–86.1 km, 0.51–0.52 km−1) and equinox (85.6–85.7 km, 0.54 km−1) seasons. The values of h′ and β during summer season are about 83.5 km and 0.60 km−1at both stations. Overall, equivalent electron density profile obtained using tweek method shows lower values of electron density by about 5–60% than those obtained using the International Reference Ionosphere (IRI-2007) model and lower/higher by 2–68% than those obtained using rocket technique. The electron density estimated using all three techniques (tweek, IRI-2007, and rocket) is consistent in the altitude range of 82–98 km. The estimated geographic locations of causative lightnings of tweeks were matched with the locations and times of lightnings detected by the World-Wide Lightning Location Network (WWLLN). The WWLLN detected about 27.5% of causative lightnings of tweeks simultaneously observed at both the stations.

[1]  M. Clilverd,et al.  Nighttime ionospheric D region parameters from VLF phase and amplitude , 2007 .

[2]  Umran S. Inan,et al.  Sensitive Broadband ELF/VLF Radio Reception With the AWESOME Instrument , 2010, IEEE Transactions on Geoscience and Remote Sensing.

[3]  Umran S. Inan,et al.  Satellite observations of lightning‐induced electron precipitation , 1998 .

[4]  Robert H. Holzworth,et al.  Detection efficiency of the VLF World-Wide Lightning Location Network (WWLLN): initial case study , 2006 .

[5]  B. Ryabov,et al.  Experimental investigation of the tweek field structure , 1992 .

[6]  U. Inan,et al.  Subionospheric VLF signatures of nighttime D region perturbations in the vicinity of lightning discharges , 1988 .

[7]  A. Aikin,et al.  Metallic ions in the equatorial ionosphere , 1973 .

[8]  Ashutosh Kumar Singh,et al.  D-region ionosphere response to the total solar eclipse of 22 July 2009 deduced from ELF-VLF tweek observations in the Indian sector , 2011 .

[9]  Umran S. Inan,et al.  Ionospheric D region electron density profiles derived from the measured interference pattern of VLF waveguide modes , 2003 .

[10]  G. Reid.  The production of water-cluster positive ions in the quiet daytime D region , 1977 .

[11]  Visagaperuman Ramachandran,et al.  Lightning stroke distance estimation from single station observation and validation with WWLLN data , 2007 .

[12]  S. Cummer,et al.  Midlatitude nighttime D region ionosphere variability on hourly to monthly time scales , 2010 .

[13]  M. Hayakawa,et al.  Polarisation effects for tweek propagation , 1998 .

[14]  H. Christian.  Global Frequency and Distribution of Lightning as Observed From Space , 2001 .

[15]  Umran S. Inan,et al.  Heating, ionization and upward discharges in the mesosphere, due to intense quasi‐electrostatic thundercloud fields , 1995 .

[16]  C. Rodger.  Subionospheric VLF perturbations associated with lightning discharges , 2003 .

[17]  A. Farmer,et al.  The solar-terrestrial environment , 1996 .

[18]  U. Inan,et al.  Ionospheric E region remote sensing with ELF radio atmospherics , 2000 .

[19]  S. Cummer,et al.  Daytime ionospheric D region sharpness derived from VLF radio atmospherics , 2011 .

[20]  N. Thomson,et al.  Nighttime ionospheric D region: Equatorial and nonequatorial , 2009 .

[21]  J. Outsu,et al.  NUMERICAL STUDY OF TWEEKS BASED ON WAVEGUIDE MODE THEORY , 1960 .

[22]  Umran S. Inan,et al.  A survey of ELF and VLF research on lightning-ionosphere interactions and causative discharges , 2010 .

[23]  Neil R. Thomson,et al.  Experimental daytime VLF ionospheric parameters , 1993 .

[24]  V. Rakov,et al.  Lightning: Physics and Effects , 2007 .

[25]  Torsten Fehr,et al.  Book Review: Rakov, V. A., M. A. Uman: Lightning: Physics and Effects. - Cambridge Univ. Press , 2005 .

[26]  S. Moreland.  The Lightning Discharge , 1890, Nature.

[27]  K. G. Budden.  The Wave-guide mode theory of wave propagation , 1963 .

[28]  K. Igarashi,et al.  D-region electron density measurements by MF radar in the middle and high latitudes , 2000 .

[29]  On ELF pulses from remote lightnings triggering sprites , 1997 .

[30]  F. Lefeuvre,et al.  The effect of subionospheric propagation on whistlers recorded by the DEMETER satellite – observation and modelling , 2007 .

[31]  M. Cohen,et al.  Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low-latitude Indian sector , 2012 .

[32]  Philip H. Scherrer,et al.  Distributing space weather monitoring instruments and educational materials worldwide for IHY 2007: The AWESOME and SID project , 2008 .

[33]  U. Inan,et al.  VLF signatures of lightning‐induced heating and ionization of the nighttime D‐region , 1993 .

[34]  S. Cummer,et al.  Midlatitude daytime D region ionosphere variations measured from radio atmospherics , 2010 .

[35]  C. Ferencz.  Real solution of monochromatic wave propagation in inhomogeneous media , 2004 .

[36]  Michiko Yamashita,et al.  Propagation of tweek atmospherics , 1978 .

[37]  S. Gupta.  Diurnal and seasonal variation of D-region electron density at low latitude , 1998 .

[38]  Umran S. Inan,et al.  Initial results from AWESOME VLF receivers: set up in low latitude Indian regions under IHY2007/UNBSSI program , 2010 .

[39]  Masashi Hayakawa,et al.  Recent findings on VLF/ELF sferics , 1995 .

[40]  S. Kumar,et al.  Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance , 2008 .

[41]  K. Maeda.  Study on Electron Density Profile in the Lower Ionosphere , 1971 .

[42]  Yasuhiro Murayama,et al.  Equivalent electron densities at reflection heights of tweek atmospherics in the low-middle latitude D-region ionosphere , 2003 .

[43]  Ashutosh Kumar Singh,et al.  Application of lightning discharge generated radio atmospherics/tweeks in lower ionospheric plasma diagnostics , 2010 .

[44]  E. Kopp.  On the abundance of metal ions in the lower ionosphere , 1997 .

[45]  M. Rycroft,et al.  Lower ionospheric modification by lightning‐EMP: Simulation of the night ionosphere over the United States , 2001 .

[46]  M. Heaps.  Parametrization of the cosmic ray ion-pair production rate above 18 km , 1978 .

[47]  Kazuo Shiokawa,et al.  Development of an automatic procedure to estimate the reflection height of tweek atmospherics , 2008 .

[48]  Umran S. Inan,et al.  On the association of terrestrial gamma‐ray bursts with lightning and implications for sprites , 1996 .

[49]  E. P. Krider,et al.  The amplitude spectra of lightning radiation fields in the interval from 1 to 20 MHz , 1986 .

[50]  James R. Wait,et al.  Characteristics of the earth-ionosphere waveguide for VLF radio waves , 1964 .

[51]  D. Baker,et al.  Nighttime D region electron density profiles and variabilities inferred from broadband measurements using VLF radio emissions from lightning , 2006 .

[52]  Masashi Hayakawa,et al.  Wave characteristics of tweek atmospherics deduced from the direction-finding measurement and theoretical interpretation , 1994 .

[53]  U. Inan,et al.  Early VLF perturbations caused by lightning EMP‐driven dissociative attachment , 2008 .

[54]  K. Shiokawa,et al.  Long‐term variations in tweek reflection height in the D and lower E regions of the ionosphere , 2011 .

[55]  D. Edemskii,et al.  Investigations of the lower ionosphere over Antarctica via ELF-VLF radiowaves , 1993, Antarctic Science.

[56]  T. Sugiyama.  Response of electrons to a gravity wave in the upper mesosphere , 1988 .

[57]  Sushil Kumar,et al.  Nighttime D-region equivalent electron density determined from tweek sferics observed in the South Pacific Region , 2009 .

[58]  Umran S. Inan,et al.  Ionospheric D region remote sensing using VLF radio atmospherics , 1998 .

[59]  K. Torkar,et al.  FIRI: A semiempirical model of the lower ionosphere , 2001 .

[60]  A. Gwal,et al.  Propagation of tweek atmospherics in the earth-ionosphere wave guide , 1994 .

[61]  R. V. Prasad.  Effects of land and sea parameters on the dispersion of tweek atmospherics , 1981 .