Attribution of interminimum changes in global and hemispheric total electron content

We use a new data product of electron column density (total electron content, or TEC) maps to estimate and attribute the interminimum changes (the differences between annual averages centered on the 2008 and 1996 solar minima) in TEC global and hemispheric averages (dividing the globe in three different ways). We attribute the observed changes to corresponding changes in solar and geomagnetic activity. The new TEC map product was constructed with temporally consistent processing, and it resolves some of the apparent inconsistencies of earlier studies. The estimated global average TEC interminimum change is −19.3% ± 1.0% (2σ uncertainty), of which −9.1% is attributable to the interminimum change in solar extreme ultraviolet (EUV) irradiance (as represented by the F10.7 index), −2.2% is attributable to the change in geomagnetic activity (Kp index), and −9.3% remains unattributed. The hemispheric results are very similar to the global results, but the values tend to be slightly larger in the Southern Hemisphere, at low latitudes, and at night, compared to the opposing respective hemispheres. The interminimum changes and temporal variations of thermospheric mass density anomalies (i.e., the difference between the data and the empirical model) are very similar to those of the global and hemispheric TEC residuals, suggesting that they are driven by a common, globally distributed mechanism. Thermospheric composition changes and additional (unobserved) decreases in solar EUV irradiance are possible mechanisms behind the TEC and mass density unattributed changes; we estimate a plausible range of −6% to −13% for the solar EUV irradiance interminimum change.

[1]  M. Paluszek,et al.  Chemical Processes , 2019, MATLAB Recipes.

[2]  J. Emmert,et al.  Thermospheric mass density: A review , 2015 .

[3]  J. Emmert.  Altitude and solar activity dependence of 1967–2005 thermospheric density trends derived from orbital drag , 2015 .

[4]  A. Coster,et al.  Ionospheric response to CIR‐induced recurrent geomagnetic activity during the declining phase of solar cycle 23 , 2015 .

[5]  J. Lean,et al.  Attribution of interminima changes in the global thermosphere and ionosphere , 2014 .

[6]  H. Le,et al.  Geomagnetic activity effect on the global ionosphere during the 2007–2009 deep solar minimum , 2014 .

[7]  D. Hathaway,et al.  The solar meridional circulation and sunspot cycle variability , 2014, 1404.5893.

[8]  J. Beer,et al.  Comparison of the extended solar minimum of 2006–2009 with the Spoerer, Maunder, and Dalton Grand Minima in solar activity in the past , 2014 .

[9]  T. Pulkkinen,et al.  Substorm occurrence during quiet solar wind driving , 2014 .

[10]  Stanley C. Solomon,et al.  Global ionospheric total electron contents (TECs) during the last two solar minimum periods , 2014 .

[11]  D. Mccomas,et al.  Coronal electron temperature in the protracted solar minimum, the cycle 24 mini maximum, and over centuries , 2014 .

[12]  P. Lamy,et al.  Comparing the solar minima of cycles 22/23 and 23/24: The view from LASCO white light coronal images , 2014 .

[13]  Stanley C. Solomon,et al.  The anomalous ionosphere between solar cycles 23 and 24 , 2013 .

[14]  K. Tapping.  The 10.7 cm solar radio flux (F10.7) , 2013 .

[15]  B. Tsurutani,et al.  The solar and interplanetary causes of the recent minimum in geomagnetic activity (MGA23): a combination of midlatitude small coronal holes, low IMF B Z variances, low solar wind speeds and low solar magnetic fields , 2011 .

[16]  W. Wan,et al.  Does the F10.7 index correctly describe solar EUV flux during the deep solar minimum of 2007-2009? , 2011 .

[17]  H. Le,et al.  The ionosphere under extremely prolonged low solar activity , 2011 .

[18]  S. Solomon,et al.  Causes of low thermospheric density during the 2007–2009 solar minimum , 2011 .

[19]  J. M. Picone,et al.  Global and regional trends in ionospheric total electron content , 2011 .

[20]  J. Picone,et al.  Climatology of globally averaged thermospheric mass density , 2010 .

[21]  T. Woods,et al.  Anomalously low solar extreme‐ultraviolet irradiance and thermospheric density during solar minimum , 2010 .

[22]  J. M. Picone,et al.  Record‐low thermospheric density during the 2008 solar minimum , 2010 .

[23]  D. Drob,et al.  A computationally compact representation of Magnetic-Apex and Quasi-Dipole coordinates with smooth base vectors , 2009 .

[24]  A. Garcia-Rigo,et al.  The IGS VTEC maps: a reliable source of ionospheric information since 1998 , 2009 .

[25]  J. Feltens,et al.  Development of a new three‐dimensional mathematical ionosphere model at European Space Agency/European Space Operations Centre , 2007 .

[26]  Michael Mendillo,et al.  Storms in the ionosphere: Patterns and processes for total electron content , 2006 .

[27]  R. Viereck,et al.  A composite Mg II index spanning from 1978 to 2003 , 2004 .

[28]  Jaume Sanz,et al.  New approaches in global ionospheric determination using ground GPS data , 1999 .

[29]  Anthony J. Mannucci,et al.  A global mapping technique for GPS‐derived ionospheric total electron content measurements , 1998 .

[30]  J. Zumberge,et al.  Precise point positioning for the efficient and robust analysis of GPS data from large networks , 1997 .

[31]  A. Richmond.  Ionospheric Electrodynamics Using Magnetic Apex Coordinates. , 1995 .

[32]  J. Bartels,et al.  International data on magnetic disturbances, first quarter, 1956 , 1956 .

[33]  J. Bartels,et al.  International data on magnetic disturbances, first quarter, 1949 , 1949 .

[34]  S. Schaer.  Mapping and predicting the Earth's ionosphere using the Global Positioning System. , 1999 .