From Correlations to Causes: Transient Energy Injection into the Polar Thermosphere

Tuesday, 16 December 2014: 11:29 AM
Herbert C Carlson1, Anasuya L Aruliah2, Asmund Skjaeveland3 and Joran Idar Moen3, (1)Utah State University, Logan, UT, United States, (2)University College London, Physics and Astronomy, London, United Kingdom, (3)University of Oslo, Physics Department, Oslo, Norway
We report data analysis, modeling, and theory leading to expectation of frequent and significant energy deposition transients in the dayside half of the polar cap. Magnetic reconnection signatures accompany them. Satellite-drag/density enhancements of 20-100% are commonly seen by CHAMP (Luhr et al, 2004). We calculate these to correspond to transient energy deposition rates at the feet of freshly reconnected open flux tubes, equaling 5-30 times solar EUV rates above 150 km altitude. That these density enhancements are observed all seasons, darkness or sunlight, IMF north or south (Kervalishvili and Luhr, 2013), is powerful evidence for ubiquitous and substantial dayside polar cap energy injection. Frictional drag heating is closest to the physical cause (Strangeway, 2011); we find response times ~ ¼ hour above 200 km. Altitude is key, Poynting flux measurements without coincident electron density profiles, can yield order of magnitude energy deposition rate errors (Richmond, 2010, Carlson et al, 2012).