Mid-latitude Electron Density Variations Under Magnetospheric Substorm Conditions As Determined From Istanbul Dynasonde Observations Aysegul Ceren MORAL, Zerefsan KAYMAZ, Emine Ceren KALAFATOGLU Istanbul Technical University, Turkey Corresponding author: moral@itu.edu.tr

Summary and Conclusions OUTLINE Purpose Data Summary and Conclusions General trends Daily variations Monthly variations Seasonal variations Substorm effects Literature work Case studies Electron density height profiles Model comparison Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

INTRODUCTION Magnetospheric substorms are the means to transfer energy from the magnetosphere into the ionosphere.  The energetic particles and auroral electrons from the magnetosphere precipitate along the field lines and deposit their energy as heat at around E-region heights, 120 kms.  This increases the ionization in the E layer and above, and the temperature as a consequence of Joule heating. In this project, we study the variations in the F2 layer under the substorm conditions, using Istanbul Dynasonde electron density observations. Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Ionosonde System at ITU The Dynasonde operating since October 2012 located within the ITU campus in Istanbul (41N, 29E) Run by Space Weather Lab at ITU ionograms at every 4 min resolution.  NeXtYZ software (Nikolay Zabotin, University of Colorado) 79 ionospheric parameters for E and F2 layers including critical frequency (foF2, foE) Critical height (hmFo, hmE) total electron content (TEC), electron density profile Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

DATA Use foF2, hmF2 and electron density (ne) Determine the storm/substorm conditions Mid-latitudes, İstanbul: Geographic Latitude: 42o, Geomagnetic Latitude: 35o The effects of substorms positive and a negative deviation from a quiet day variation. Dst < -40 nT disturbed i.e. Storm conditions AE > 100 nT disturbed, Auroral substorn conditions Studied two cases where we have seen the positive and negative phases Preliminary results are presented Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Examples from Literature TEC contours Latitudes from Narssarssuaq (63o) Goose Bay (60o) Sagamore Hill (54o) KSFC (42o) 4 days interval Subtract: Storm day-Quiet day Positive phase (Red contours) Higher density than that in quiet day 1 day Negative phase (Blue contours): Lower density than that in quiet day 3 day Mendillo, 2006, Reviews of Geophysics, 44, RG4001 Positive phase Negative phase İstanbul Geomagnetic Latitude (35o) Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Substorm Signatures Classified the signatures observed during substorms 5 types were recognized Prölls, G.W., (1995), In Handbook of Electrodynamics, vol.2, ed. H.Holland Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

General trends Daily Monthly Seasonal Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

AN EXAMPLE IONOGRAM: 21 April 2013 09 UT 12 LT 21 UT 00 LT Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

MONTHLY VARIATION: f0F2 2012 foF2 Sep Nov Oct May Apr Mar Jun Jul Aug Feb Jan Dec Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

SEASONAL VARIATION 2012 f0F2 foF2 hmF2 foF2 High daytime electron density at spring noon Lowest night time electron density during winter nights Lowest daytime electron density in summer High fluctuations in summer hmF2 Lowest hegihts during summer daytime Fall Spring Winter Summer Fall Spring Winter Summer Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Storm/Substorm Relation Using Dst and AE magnetic indices, we have determined two strong magnetospheric substorm Then we selected a very quiet day We investigated the variations in foF2 and TEC for these two days by subtracting the quiet day variation from disturbed day variation Dif=Disturbed – Quiet Positive differences mean foF2 is higher during disturbed days Negative differences mean foF2 during disturbed days is lower than foF2 observed during quiet day. Case selection is based on Dst < -40 nT  Storm AE > 100 nT  Auroral Substorm Dif > 0  Positive Phase Dif < 0  Negative Phase Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

CASE 1: 17 MARCH 2013 Positive phase Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

CASE 1: 17 MARCH 2013 Difference 12 UT Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

CASE 2: 14 NOVEMBER 2012 Positive phase Negative phase Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

CASE 2: 14 NOVEMBER 2012 Difference Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Differences Positive Phase Negative Phase Time UT Dst AE Dif. foF2 4 -10 42 -0.07 6 -7 111 -0.08 13 -88 986 2.29 18 -99 1452 0.56 21 -132 836 1.11 Positive Phase Time UT Dst AE Dif. foF2 3 -77 936 0.17 4 -92 1009 0.65 9 -100 627 -2.18 12 -73 152 -0.87 18 -50 63 0.96 Negative Phase Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Electron density Height Profiles: Comparisons with models Case-1: March 17, 2012 Positive phase IRI: International Reference Ionosphere TIEGCM: Thermosphere Ionosphere Electrodynamics General Circulation Model

Electron Density Height Profiles: Comparisons with models Case-2: Nov 13-14 2012 Negative phase Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

SUMMARY & CONCLUSIONS Preliminary results from Istanbul, Turkey, Dynasonde foF2 variations: daily, monthly, seasonal High fluctuations both in foF2 and hmF2 are seen during the summer months with less electron density compared to those of winter time. Indicating the role of the atmospheric dynamics during the summer months Storm/substorm effects on ionospheric density over Istanbul, a midlatitude station Presented 2 Case study (Disturbed – Quiet) day differences Positive/negative differences corresponding to changes in Dst and AE Positive phase  1 day or a little over 1 day (extending to the next day) Electron densities are higher by about %17 during positive phase at 12:00 UT noon Largest differences were found during the mid-day (12 noon) and afternoon times extending toward dusk (06 UT) Negative phase  1 day Electron densities are lower by about %17 during negative phase at 09:00 UT Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

SUMMARY & CONCLUSIONS Future Work; Height profiles were compared with model results. IRI underestimates height of the peak electron density closer to the observations These are expected as the model does not include magnetosphere-ionosphere coupling TIEGCM model gives closer agreement with observations during the positive phase of the storms It overestimates the height of the electron density peak during the positive phase TIEGCM overestimates both the peak electron density and the height during the negative phase of the substorms Future Work; Statistical studies on the response of the ionosphere to substorms still continue 2012 and 2013 complete statistics Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

ACKNOWLEGDEMENTS This study has been supported by Turkish Scientific and technological Council (TUBITAK), project No= 113Y213 Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014

Thank you for your attention !... Moral, Kaymaz, Kalafatoglu AOGS 2014 Sapporo Japan 28 July-1 Aug 2014