Searching for relationships between the solar regular daily magnetic variation at mid latitude and the solar irradiance at different ionizing wavelengths Elena Saiz, J. Palacios, A. Guerrero, C. Cid, Y. Cerrato Space Research Group - Space Weather University of Alcalá (Spain) elena.saiz@uah.es

Linking some ideas What is the solar regular daily magnetic variation, SR? The quiet-time magnetic response measured at ground and associated to Sq current system generated in E layer of the ionosphere by dynamo action What is its primary origin? The solar irradiance that generates ionospheric ionization EUV, XR,…. Image taken from the web site:  www.geomag.bgs.ac.uk/earthmag.html Why study SR at mid-latitude locations? Because of its strong day-to-day variability → not easy to determine, especially at latitudes close to vortex focus Why is important and necessary to find empirical solar irradianceSR relationships? To obtain the actual magnetic disturbance when elaborating magnetic indices To monitor magnetic conditions through real-time local indices and forecast for space weather purposes

Plannig our work… Searching for quiet-time magnetic response at ground Searching for solar ionizing irradiance at several wavelengths 5 monthly International quiet days (IQDs) of at least one solar cycle http://www.ga.gov.au/oracle/geomag/iqd_form.jsp EUV flux PROBA2/LYRA: C3 [Al] (17-80) , C4 [Zr] (6-20) nm http://proba2.oma.be/lyra/data/bsd/ X-R flux GOES/XRS: A (0.05-0.4) and B (0.1-0.8 ) nm http://satdat.ngdc.noaa.gov/sem/goes/data/new_full/ Quiet day curve (SR) of those IQDs at SPT observatory (Spain), close to northern Sq focus Obtained by fitting a model used to elaborate the real-time local index (LDiñ) for Spain F10.7 flux http://omniweb.gsfc.nasa.gov/form/dx1.html mean daily fluxes SR_ H amplitude

A quick first sampling “White solar days” (without sunspots/with a minimun number of solar regions) (1-4 July 2016 as an example) Monthly IQDs (April 2015 as an example) It seems there is not relationship! neither! Might it be because a magnetic quiet day does not seem to be a solar quiet day? Even more, any day of this period is IQD!

And some more periods included but… Conclusions Changing season (winter), solar cycle phase (minimum) and “white solar days” period: Dec. 2015, Ap & Dec 2008, 1-4 Jun 2016 respectively From this preliminary study, no direct relationship SR amplitude – flux intensity has been found. These results and the great volume of data to be handled make the task of surveying this effect along solar cycles difficult We think the result comes from other causes other than ionizing solar irradiance which can mask its effect and strongly contribute to the “regular” daily magnetic response (and its day- to-day variability); causes of terrestrial (e.g telluric induced currents, oceanic effect, …), thermospheric (e.g. waves from lower atmosphere, conductivity,…) magnetospheric (e.g. distant magnetospheric currents), interplanetary (e.g. IMF polarity, fast wind from CHs, periods of enhanced solar wind pressure) and solar origin (e.g. through flaring activity as well as presence of CHs with effect some days later). To the already short- and medium-term complex scenario another difficulty is added because some of them present periodicities The combined effects change global thermotidal winds and magnetic field, so changing the currents of the dynamo region