Earthq Sci (2011)24: – 1 doi: Atmosphere-ionosphere response to the M 9 Tohoku earthquake revealed by multi- instrument space-borne and ground observations: Preliminary results Ouzounov Dimitar 1,2, Pulinets Sergey 3,5 Romanov Alexey 4 Romanov Alexander 4 Tsybulya Konstantin 3 Davidenko Dmitri 3 Kafatos Menas 1 and Taylor Patrick 2 1 Department of Physics, Chapman University, Orange, CA 92866, USA 2 NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 3 Institute of Applied Geophysics, Moscow 129128, Russia 4 Russian Space Systems, Moscow 111250, Russia 5 Space Research Institute RAS, Moscow 117997, Russia Abstract We retrospectively analyzed the temporal and spatial variations of four different physical param- eters characterizing the state of the atmosphere and ionosphere several days before the M9 Tohoku, Japan earthquake of March 11, 2011. The data include outgoing long wave radiation (OLR), GPS/TEC, lower Earth orbit ionospheric tomography and critical frequency foF2. Our first results show that on March 7th a rapid in- crease of emitted infrared radiation was observed from the satellite data and an anomaly developed near the epicenter. The GPS/TEC data indicate an increase and variation in electron density reaching a maximum value on March 8. Starting from this day in the lower ionosphere also there was confirmed an abnormal TEC variation over the epicenter. From March 3 to 11 a large increase in electron concentration was recorded at all four Japanese ground-based ionosondes, which returned to normal after the main earthquake. The jointly preliminary analysis of atmospheric and ionospheric parameters during the M9 Tohoku, Japan earthquake has revealed the presence of related variations of these parameters implying their connection with the earthquake process. This study may lead to a better understanding of the response of the atmosphere/ionosphere to the great Tohoku earthquake. Key words: Tohoku earthquake; thermal anomaly; GPS/TEC; earthquake precursor; early warning CLC number: P315.72 + 1 Document code:A 1 Introduction The M 9 Tohoku earthquake on March 11, 2011 was followed by a large number of powerful after- shocks. The possibility of a mega-earthquake in Miya- gi prefecture was initially discussed by Kanamor- i et al. (2006). Strong earthquakes in this region were recorded since 1793 with average period of 37±7 years. The latest great Tohoku earthquake matched this reoccurrence period since the last one * Received 22 May 2011; accepted in revised form 19 September 2011; published 10 October 2011. Corresponding author. e-mail: ouzounov@chapman.edu The Seismological Society of China and Springer-Verlag Berlin Heidelberg 2011 occurred in 1978. Figure 1 shows the location of To- hoku earthquake and data receivers as well as vertical ionosonde stations in Japan. The observational evidence from the last twenty years, provide a significant pattern of transient anoma- lies preceding earthquakes (Tronin et al., 2002; Liu et al., 2004; Pulinets and Boyarchuk, 2004; Tramu- toli et al., 2005, Parrot, 2009, Oyama et al., 2011). Several of the papers indicated that atmospheric vari- ation was also detected prior to an earthquake. De- spite these pre-earthquake atmospheric transient phe- nomenon (Ouzounov et al., 2006, 2007; Inan et al., 2008; N˘ emec et al., 2009; Pulinets et al., 2009; Kon et al., 2010), there is still lack of consistent data necessary to