Two‐dimensional observations of midlatitude sporadic E irregularities with a dense GPS array in Japan

[1] We observed two-dimensional structure and time evolution of ionospheric irregularities caused by midlatitude sporadic E (Es) over Japan as positive anomalies of total electron content (TEC) by analyzing the data from the nationwide Global Positioning System (GPS) array. In this paper we report a case study of strong Es observed in the local evening of 21 May 2010, over Tokyo, Japan. In the slant TEC time series, Es showed a characteristic pulse-like enhancement of ~1.5 TEC units lasting for ~10 min. We plotted these positive TEC anomalies on the subionospheric points of station-satellite pairs to study the horizontal structure of the Es irregularity. We confirmed that the irregularity existed at the height of ~106 km by comparing the data of multiple GPS satellites, which is consistent with the local ionosonde observations. The horizontal shapes of the Es irregularity showed frontal structures elongated in E-W, spanning ~150 km in length and ~30 km in width, composed of small patches. The frontal structure appears to consist of at least two parts propagating in different directions: one moved eastward by ~60 m s−1, and the other moved southwestward by ~80 m s−1. Similar TEC signatures of Es were detected by other GPS satellites, except one satellite that had line of sight in the N-S direction which dips by 40–50° toward north, which indicates the direction of plasma transportation responsible for the Es formation. We also present a few additional observation results of strong Es irregularities.

[1]  Vladislav V. Kiryushkin,et al.  Two‐mode long‐distance propagation of coseismic ionosphere disturbances , 2009 .

[2]  R. Tsunoda,et al.  A direction‐dependent instability of sporadic‐E layers in the nighttime midlatitude ionosphere , 2002 .

[3]  J. Ping,et al.  Directivity and apparent velocity of the coseismic ionospheric disturbances observed with a dense GPS array , 2005 .

[4]  Mamoru Yamamoto,et al.  Mid‐latitude E region field‐aligned irregularities observed with the MU radar , 1991 .

[5]  L. Smith,et al.  Horizontal structure of midlatitude sporadic‐E layers observed by incoherent scatter radar , 1975 .

[6]  L. Smith,et al.  Incoherent scatter radar observations of irregular structure in mid‐latitude sporadic E layers , 1978 .

[7]  J. Meriwether,et al.  Testing the thermospheric neutral wind suppression mechanism for day-to-day variability of equatorial spread F , 2001 .

[8]  H. Hayakawa,et al.  SEEK-2 (Sporadic-E Experiment over Kyushu 2) − Project Outline, and Significance , 2005 .

[9]  J. Whitehead.  Recent work on mid-latitude and equatorial sporadic-E , 1989 .

[10]  T. Yokoyama,et al.  Three‐dimensional simulation of the coupled Perkins and Es‐layer instabilities in the nighttime midlatitude ionosphere , 2008 .

[11]  Mamoru Yamamoto,et al.  Gravity wave modulation of gradient drift instabilities in mid-latitude sporadic E irregularities , 1991 .

[12]  M. Yamamoto,et al.  Observations of neutral winds, wind shears, and wave structure during a sporadic- E /QP event , 2005 .

[13]  J. Mathews.  Sporadic E: current views and recent progress , 1998 .

[14]  Takashi Tanaka.  Sky-wave backscatter observations of sporadic-E over Japan , 1979 .

[15]  M. Yamamoto,et al.  Radio tomographic imaging of sporadic- E layers during SEEK-2 , 2005 .

[16]  P. Bernhardt,et al.  Electron density and plasma waves in mid-latitude sporadic- E layer observed during the SEEK-2 campaign , 2005 .

[17]  G. G. Bowman.  Movements of ionspheric irregularities and gravity waves , 1968 .

[18]  S. Fukao,et al.  Observations of traveling ionospheric disturbances and 3-m scale irregularities in the nighttime F-region ionosphere with the MU radar and a GPS network , 2002 .

[19]  Jens Wickert,et al.  Semidiurnal tidal signature in sporadic E occurrence rates derived from GPS radio occultation measurements at higher midlatitudes , 2009 .

[20]  R. Cosgrove.  Wavelength dependence of the linear growth rate of the E s layer instability , 2006 .

[21]  Kosuke Heki,et al.  Explosion energy of the 2004 eruption of the Asama Volcano, central Japan, inferred from ionospheric disturbances , 2006 .

[22]  J. Whitehead.  The Structure of Sporadic E From a Radio Experiment , 1972 .

[23]  T. Tsuda,et al.  A global distribution of sporadic E events revealed by means of CHAMP-GPS occultations , 2006 .

[24]  J. D. WHITEHEAD,et al.  Formation of the Sporadic E Layer in the Temperate Zones , 1960, Nature.

[25]  T. Yokoyama,et al.  Numerical simulation of mid-latitude ionospheric E-region based on SEEK and SEEK-2 observations , 2005 .

[26]  S. Nozawa,et al.  Horizontal structure of sporadic E layer observed with a rocket‐borne magnesium ion imager , 2010 .

[27]  T. Ogawa,et al.  Azimuth‐dependent Es layer instability: A missing link found , 2004 .

[28]  Masaru Ozeki,et al.  Ionospheric holes made by ballistic missiles from North Korea detected with a Japanese dense GPS array , 2010 .

[29]  J. Whitehead.  Production and prediction of sporadic E , 1970 .

[30]  M. Yamamoto,et al.  Structures in sporadic‐E observed with an impedance probe during the SEEK Campaign: Comparisons with neutral‐wind and radar‐echo observations , 1998 .

[31]  T. Maruyama.  Shapes of irregularities in the sporadic E layer producing quasi-periodic scintillations , 1995 .

[32]  Michael B. Heflin,et al.  The effect of the second order GPS ionospheric correction on receiver positions , 2003 .

[33]  Keisuke Hosokawa,et al.  Large‐scale traveling ionospheric disturbance observed by superDARN Hokkaido HF radar and GPS networks on 15 December 2006 , 2010 .

[34]  Takuya Tsugawa,et al.  A statistical study of large-scale traveling ionospheric disturbances using the GPS network in Japan , 2004 .

[35]  Paul A. Bernhardt,et al.  The modulation of sporadic-E layers by Kelvin–Helmholtz billows in the neutral atmosphere , 2002 .

[36]  L. B. Kolawole,et al.  Skywave backscatter studies of temperate latitude Es , 1977 .

[37]  G. G. Bowman.  Some aspects of Sporadic-E at mid-latitudes , 1960 .

[38]  M. Larsen,et al.  A shear instability seeding mechanism for quasiperiodic radar echoes , 2000 .

[39]  T. Maruyama.  Observations of quasi‐periodic scintillations and their possible relation to the dynamics of Es plasma blobs , 1991 .

[40]  C. Reddy,et al.  On the physical significance of the Es parameters ƒbEs, ƒEs, and ƒoEs , 1968 .

[41]  R. Tsunoda,et al.  Coupled electrodynamics in the nighttime midlatitude ionosphere , 2001 .

[42]  T. Ono,et al.  Multi-layer structure of mid-latitude sporadic- E observed during the SEEK-2 campaign , 2005 .

[43]  M. Larsen,et al.  The SEEK Chemical Release Experiment: Observed neutral wind profile in a region of sporadic E , 1998 .