High-latitude ionospheric monitoring by incoherent scatter radar: Casestudies for mitigation of space weather effects on satellite navigationCarl-Fredrik Enell, Anders Tjulin, Ingemar Häggström and Michael T. Rietveld, EISCAT Scientific Association, Kiruna, SwedenThe European Incoherent Scatter Scientific Association (EISCAT) studies the ionosphere usingincoherent scatter radars (ISR) and complementary instruments (dynasondes and a HF radar andheating facility). The locations of the EISCAT instruments in northern Europe are shown below.80Backscatter power7080Electron density LongyearbyenIon temperature75Electron temperatureIon drift velocity7050Latitude [N]60Radar, Dynasonde40 TromsoUHF, VHF, HF, Dynasonde 100102030Longitude [E]40Kiruna SodankylaRemote Rx Remote Rx5065Latitude [N]EISCAT is funded by institutes in China, Finland,Germany, Japan, Norway, Sweden and the UK (theEISCAT Associates).The radars are operated according to a campaignschedule whereas the dynasondes run at 2-minuteintervals. From the ISR data analysis the followingparameters can be estimated directly or throughsimple unit conversions:0102030Longitude [E]Enell et al (EISCAT)4050The dynasonde analysis also produces electrondensity profiles and several other parameters.EISCAT provides data for selected events to the FP7Mitigation of Space Weather Threats to GNSSServices (MISW) project ( ionospheric measurementsESWW111/5

IPY 2007 EISCAT Svalbard radar runThe EISCAT Svalbard radar was operated almost continuously during the international polar year 2007–2008.The figure below shows an overview of electron density profiles calculated from ion line measurements withthe 42 m field-aligned antenna. Also shown is the Ap index (from NOAA SWPC) as an indicator of spaceweather events.This comprehensive dataset contains data from all seasons and different atmospheric and space weatherconditions.Overview March-December 2007Enell et al (EISCAT)High-latitude ionospheric measurementsESWW112/5

Retrieved and raw electron densityThe following figures show two measures of electron density Ne : fitted as parameter of theoretical spectrum,and estimated raw power in units of equivalent Ne . The latter raw Ne is available also from the lowermostionosphere, where incoherent scatter theory is not applicable.1 April 2007Enell et al (EISCAT)25 May 2007High-latitude ionospheric measurements20 October 2007ESWW113/5

TEC estimates from ionosonde and incoherent scatter radarHF radars are operated atthe Tromsø andLongyearbyen sites. TheDSND analysis process (N.Zabotin, U. Colorado)provides true heightprofiles of electron density.Integration of radarprofilesComparison for two MISW events519:0020:0021:0022:0023:0000:00UTTEC [10km10EISCAT Svalbard 2012-11-1620500LR dynasonde 2012-10-17 21:00 UT15018:0016ESR 42m beataPolynomial fit600ESR 42m beataDynasondem -2 ]Estimated TEC: 3.853 17-Oct-2012 21:00:30700EISCAT Svalbard 2012-10-1720Line integrals of radarelectron density must becalculated on smoothprofiles. In these examples,polynomials were fitted tothe height profiles ofanalysed electron densityand integrated in the range70–700 km.TEC [10 16 m -2 ]Dynasonde analysis400300ESR 42m taroESR 42m beataDynasonde15105200TEC is also anautomatically calculateddata product.Enell et al 009:0010:0011:0012:0013:00UT99.510log 10 (N e /m10.5-31111.5)High-latitude ionospheric measurementsESWW114/5

Summary and conclusionsIncoherent scatter radars and dynasondes canprovide measures of total electron content formitigation of space weather effects on satellitenavigation. The results in the presented casestudies are of the same order of magnitude butnot directly comparable (due to different slantline of sight directions, etc).The instruments also provide slant profiles ofelectron density for a more exact calculation ofsignal delays. Dedicated measurements areplanned.Analysed electron density profiles are usuallygood in the E and F regions. During severespace weather events the raw electron densitiesare also useful for better estimates of D regioneffects.Enell et al (EISCAT)More informationEISCAT http://www.eiscat.seMISW FP7 http://misw.infoData available http://www.espas-fp7.euIonosonde data be changed)High-latitude ionospheric measurementsESWW115/5

High-latitude ionospheric monitoring by incoherent scatter radar: Case studies for mitigation of space weather effects on satellite navigation Carl-Fredrik Enell, Anders Tjulin, Ingemar Häggström and Michael T. Rietveld, EISCAT Scientific Association, Kiruna, Sweden . Remote Rx EISCAT is funded by institutes in China, Finland, Germany .