On the ionospheric and thermospheric response of solar flare events of 19 January 2005: An investigation using radio and optical techniques

This study presents optical signatures of thermospheric OI 630.0 nm dayglow variability over a geomagnetic dip equatorial station Trivandrum (8.5°N, 77°E, 0.5° dip latitude), India, in response to solar flares of different ranks that occurred on 19 January 2005. It is found that over equator, the response of thermospheric dayglow to solar flares can be either prompt or delayed depending upon rank of the flare and dominant neutral/electrodynamical processes prevailing in the emission altitudes. This is strikingly in contrast to the earlier results, where prompt response of equatorial OI 630.0 nm dayglow to solar flares has been noticed. In addition, the flare‐induced changes at the E and F regions of the equatorial ionosphere are studied using high‐cadence measurements of the equatorial electrojet (EEJ) and total electron content (TEC) obtained from the ground‐based magnetometers and GPS receivers, respectively. The Hall/Pedersen conductivity measurements as inferred using the magnetometers over the EEJ station and an off‐EEJ station showed concomitant changes during these flares. Although, the GPS‐measured TEC showed prompt enhancement associated with these flares, the evolution of the equatorial ionization anomaly, as seen in the TEC did not show any flare‐induced changes. The plausible mechanisms explaining these observations are adduced in context of the present understanding of the equatorial electrodynamics and its imprint on these dayglow features.

[1]  T. Pant,et al.  Signatures of Sudden Stratospheric Warming on the Equatorial Ionosphere-Thermosphere System , 2012 .

[2]  A. Burns,et al.  Solar flare impacts on ionospheric electrodyamics , 2012 .

[3]  H. Le,et al.  Statistical analysis of solar EUV and X-ray flux enhancements induced by solar flares and its implication to upper atmosphere , 2011 .

[4]  T. Pant,et al.  Response of the tropical mesopause to the longest annular solar eclipse of this millennium , 2011 .

[5]  Zuo Xiao,et al.  Impact factor for the ionospheric total electron content response to solar flare irradiation , 2011 .

[6]  C. Vineeth,et al.  A new insight into the vertical neutral-ion coupling between the mesopause and equatorial ionosphere F-region , 2011 .

[7]  N. Lodhi,et al.  Observations of X-ray and EUV fluxes during X-class solar flares and response of upper ionosphere , 2010 .

[8]  S. Chakrabarti,et al.  Effect of an X-Class Solar Flare on the OI 630 nm Dayglow Emissions , 2010 .

[9]  T. Pant,et al.  Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 - a case study , 2009 .

[10]  T. Pant,et al.  Signatures of low latitude–high latitude coupling in the tropical MLT region during sudden stratospheric warming , 2009 .

[11]  A. Ridley,et al.  Modeling the thermospheric response to solar flares , 2008 .

[12]  P. Alken,et al.  Estimating the daytime Equatorial Ionization Anomaly strength from electric field proxies , 2008 .

[13]  S. Thampi,et al.  Investigation on the mesopause energetics and its possible implications on the equatorial MLTI processes through coordinated daytime airglow and radar measurements , 2007 .

[14]  Hermann Lühr,et al.  Contrasting behavior of the thermosphere and ionosphere in response to the 28 October 2003 solar flare , 2007 .

[15]  E. Sutton,et al.  Neutral density response to the solar flares of October and November, 2003 , 2006 .

[16]  P. V. S. Rama Rao,et al.  On the validity of the ionospheric pierce point (IPP) altitude of 350 km in the Indian equatorial and low-latitude sector , 2006 .

[17]  Chien-Hung Lin,et al.  Solar flare signatures of the ionospheric GPS total electron content , 2006 .

[18]  K. Viswanathan,et al.  Response of the equatorial electrojet to solar flare related X-ray flux enhancements , 2005 .

[19]  A. Mannucci,et al.  The October 28, 2003 extreme EUV solar flare and resultant extreme ionospheric effects: Comparison to other Halloween events and the Bastille Day event , 2005 .

[20]  G. Shepherd,et al.  Solar influence on the O(1D) dayglow emission rate: Global‐scale measurements by WINDII on UARS , 2004 .

[21]  J. Huba,et al.  Ionospheric response to the solar flare of 14 July 2000 , 2004 .

[22]  N. Østgaard,et al.  Effect of the 14 July 2000 solar flare on Earth's FUV emissions , 2003 .

[23]  J. Lean,et al.  Ionospheric and dayglow responses to the radiative phase of the Bastille Day flare , 2002 .

[24]  J. Olson,et al.  Assimilated observations of thermospheric winds, the aurora, and ionospheric currents over Alaska , 2001 .

[25]  R. Sridharan,et al.  High resolution 2-D maps of OI 630.0 nm thermospheric dayglow from equatorial latitudes , 1998 .

[26]  T. Pant,et al.  A multiwavelength daytime photometer - a new tool for the investigation of atmospheric processes , 1998 .

[27]  R. Sridharan,et al.  Precursor to equatorial spread-F in OI 630.0 nm dayglow , 1994 .

[28]  S. Solomon,et al.  The 630 nm dayglow , 1989 .

[29]  T. Killeen,et al.  An analysis of the high‐latitude thermospheric wind pattern calculated by a thermospheric general circulation model: 1. Momentum forcing , 1984 .

[30]  J. Forbes.  The equatorial electrojet , 1981 .

[31]  T. Woods,et al.  Solar ultraviolet variability during the TIMED mission , 2004 .

[32]  Yuei-An Liou,et al.  Ionospheric solar flare effects monitored by the ground‐based GPS receivers: Theory and observation , 2004 .

[33]  T. Pant,et al.  Plausible explanation for the equatorial temperature and wind anomaly (ETWA) based on chemical and dynamical processes , 2001 .

[34]  M. Sivaraman,et al.  CORRELATION OF THE IONISATION ANOMALY WITH THE INTENSITY OF THE ELECTROJET , 1978 .

[35]  D. Cunnold.  The equatorial electrojet. , 1978 .