the manicouagan impact structure an analysis of its original dimensions and form manicouagan quebec 51 23 n 68 42 w is the most intensively studied large complex terrestrial impact structure in a predominantly crystalline target the ground truth data available from manicouagan have considerable potential for interpreting the subsurface characteristics of lunar impact structures of comparable morphology and size two contrasting hypotheses however exist for the preerosional form of manicouagan 1 a multi ring basin with a final diameter of 75 km and a transient cavity diameter of 30 45 km floran and dence 1976 and 2 an endogenically modified peak ring basin with a final diameter of 100 km and a transient cavity diameter of 80 km orphal and schultz 1978 both hypotheses are based largely on topographic data and interpret the prominent 65 km diameter annular moat as a graben like feature formed either 1 by collapse of the outer slope of the transient cavity rim or 2 by uplift of the final crater floor through post impact intrusive activity the present analysis suggests that this annular moat is primarily an erosional feature and that the original form of the impact structure cannot be determined unequivocally on the basis of present topography if all the available topographic geologic and geophysical data are considered however then an internally consistent interpretation of original dimensions is possible the distribution of shock deformation effects in the basement rocks of the present crater floor suggests an original transient cavity diameter of 60 km the 55 km diameter impact melt covered inner plateau provides a minimum estimate for the diameter of the final floor of the crater and the annular moat with its outliers of downdropped ordovician limestone is interpreted as marking the contact between the floor and the innermost slump blocks of the final rim there is no compelling evidence to regard the annular moat as a graben by analogy with fresh lunar and mercurian structures a floor width of 55 km suggests a final rim diameter of 86 95 km this is consistent with the topographic data from outside the annular moat and with the residual peripheral gravity low which suggests a final rim diameter of 85 95 km due to erosion it is difficult to assign manicouagan to a particular morphological class of impact structure but on the basis of the available data it is most likely that the preerosional form was that of a central peak crater or possibly a peak ring basin at the time of its formation manicouagan may have been dimensionally and possibly morphologically similar to the 96 km diameter lunar crater copernicus

equatorial vertical drift modulation by the lunar and solar semidiurnal tides during the 2013 sudden stratospheric warming during the 2013 stratospheric sudden warming ssw period the jicamarca unattended long term investigations of the ionosphere and atmosphere julia radar at jicarmarca peru observed low latitude vertical drift modulation with lows of 0 12 m s daytime maximum drifts between 6 13 and 22 25 january and enhanced drifts up to 43 m s between 15 snd 19 january the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model reproduces the prevailing vertical drift feature and is used to examine possible causes the simulations indicate that the modulation of the vertical drift is generated by the beating of the semidiurnal solar sw2 and lunar m2 tides during the ssw period the beating is observable since the magnitudes of lunar and solar semidiurnal tidal amplitudes are comparable the theoretical beating frequency between sw2 and m2 is 1 15 13 day which may be modified due to phase changes this study highlights the importance of the lunar tide during ssw periods and indicates that the equatorial vertical drift modulation should be observable at other longitudes as well

the lappajarvi meteorite crater finland petrography rb sr major and trace element geochemistry of the impact melt and basement rocks abstract impact melt lithologies of the 77 m y old finnish meteorite crater lappajarvi as well as the precambrian target rocks have been studied in detail to identify and characterize different impact melt types clast poor clast rich suevitic melt and to study their chemical major and trace elements and isotopic rb sr compositions in comparison to the composition of the target rocks the rb sr system of the whole melt body including the suevitic melt is shown to have been reequilibrated by the impact by extensive turbulent mixing of the various melted or vaporized target rocks chemical interactions exchange of alkali elements 87sr redistribution between feldspar clasts and impact melt surrounding them are the result of thermal metamorphism following the incorporation of target rock fragments of various degrees of shock metamorphism into the superheated melt exchange reactions between clasts and melt are determined by thermal activation but the degree of shock metamorphism in the clasts plays an important role too major and trace element distributions in impact melt and basement rocks indicate that the lappajarvi melt body chemically is extremely homogeneous even volatile elements such as zn and cu were not strongly fractionated comparison of the abundances of siderophile elements in the impact melt e g 118 177 ppm cr 195 340 ppm ni 6 12 ppb ir and calculated target rock mixture 79 mica schist 11 granite pegmatite 10 amphibolite e g 85 6 ppm cr 54 8 ppm ni 0 5 ppb ir revealed the chondritic nature c or h chondritic of the meteoritic projectile less than 2 of the meteorite can be detected in the coherent melt whereas the suevitic melt is uncontaminated by the projectile

chromium isotopic studies of terrestrial impact craters identification of meteoritic components at bosumtwi clearwater east lappajarvi and rochechouart chromium isotopic compositions and elemental abundances in impact melt rock and impact glass samples from four terrestrial impact craters were measured to verify the presence of an extraterrestrial component and to identify the meteorite type of the impactor all meteorite classes have cr isotopic signatures that are different from those of terrestrial rocks thus precise measurements of cr isotopic abundances can unequivocally distinguish terrestrial from extraterrestrial materials for all four studied craters bosumtwi ghana clearwater east canada lappajarvi finland and rochechouart france we found positive 53cr excesses that eliminate carbonaceous chondrite projectiles because those would show apparent negative excesses and enstatite chondrites because of the magnitude of the excess in all four cases ordinary chondrites have been identified as the best fit for the data in the case of lappajarvi interelement correlations together with the cr isotope data make an h chondrite the most likely projectile whereas in the case of clearwater east both l or h chondrites are possible for bosumtwi and rochechouart the high indigenous contents of the siderophile elements and disturbances of the elemental abundances by weathering and hydrothermal alteration respectively do not allow further constraints to be placed on the type of ordinary chondrite involved in the impact

the lappajarvi impact structure finland age duration of crater cooling and implications for early life abstract an in depth approach of 40 ar 39 ar dating of the 23 km lappajarvi impact structure finland was performed using carefully selected single grain aliquots of optically fresh clast poor impact melt rock and recrystallized k feldspar melt particles separated from impact metamorphosed granite pegmatite step heating analysis yielded a set of 13 statistically robust plateau ages obtained on six melt rock and seven k feldspar samples the melt rocks yielded fully concordant ages with a weighted mean of 76 37 0 46 ma dating of the k feldspar melt particles resulted in a series of younger plateau ages ranging from 75 11 0 36 to 76 11 0 35 ma the melt rock results combined with the oldest syn melt rock k feldspar age and including all sources of uncertainties yielded a weighted mean age of 76 20 0 29 ma 2 mswd 1 02 p 0 41 which is interpreted to represent the best estimate age of the lappajarvi impact the age spread of at least 1 1 0 5 ma between the crystallization of the impact melt rocks and the k feldspar melt particles warns against the use of single 40 ar 39 ar analysis to derive a meaningful impact age in turn the age offset monitors both rapid cooling of the lappajarvi melt sheet versus slow cooling and impact induced hydrothermal circulation within the crater basement most likely driven by long lasting heat flow from the hot central uplift of the impact structure this interpretation is in line with the grain size dependent argon diffusion parameters and apparent closure temperatures of 230 410 c determined for various domain sizes of k feldspars observed in this study our study shows that even in comparatively small impact craters post impact hydrothermal activity can be estimated to last between 600 ka and 1 6 ma and is technically resolved by means of the 40 ar 39 ar dating technique therefore the longevity of hydrothermal systems in medium sized impact craters might be an order of magnitude longer than previously estimated prolonged post impact heat flow in medium sized craters in analogy to lappajarvi might have played an important role in the emergence of life on early earth and possibly mars

f2 region response to geomagnetic disturbances across indian latitudes o 1s dayglow emission the morphology of ionospheric storms has been investigated across equatorial and low latitudes of indian region the deviation in f 2 region characteristic parameters f o f 2 and hf along with modeled green line dayglow emission intensities is examined at equatorial station thiruvananthapuram 8 5 degrees n 76 8 degrees e 0 63 degrees s geomagnetic latitude and low latitude station delhi 28 6 degrees n 77 2 degrees e 19 2 degrees n geomagnetic latitude during five geomagnetic storm events both positive and negative phases have been noticed in this study the positive storm phase over equatorial station is found to be more frequent while the drop in ionization in most of the cases was observed at low latitude station it is concluded that the reaction as seen at different ionospheric stations may be quite different during the same storm depending on both the geographic and geomagnetic coordinates of the station storm intensity and the storm onset time modulation in the f 2 layer critical frequency at low and equatorial stations during geomagnetic disturbance of 20 23 november 2003 was caused by the storm induced changes in o n 2 it is also found that international reference ionosphere 2012 model predicts the f 2 layer characteristic f o f 2 and hf parameters at both the low and equatorial stations during disturbed days quite reasonably a simulative approach in glow model developed by solomon is further used to estimate the changes in the volume emission rate of green line dayglow emission under quiet and strong geomagnetic conditions it is found that the o s 1 dayglow thermospheric emission peak responds to varying geomagnetic conditions

radiation and atmospheric circulation controls on carbonyl sulfide concentrations in the marine boundary layer a potential closure of the global carbonyl sulfide cos or ocs budget has recently been attained through a combination of remote sensing modeling and extended surface measurements however significant uncertainties in the spatial and temporal dynamics of the marine flux still persist in order to isolate the terrestrial photosynthetic component of the global atmospheric ocs budget tighter constraints on the marine flux are needed we present 6 months of nearly continuous in situ ocs concentrations from the north atlantic during the fall and winter of 2014 2015 using a combination of research vessel and fixed tower measurements the data are characterized by synoptic scale 100 pmol mol 1 variations in marine boundary layer air during transitions from subtropical to midlatitude source regions the synoptic ocs variability is shown here to be a linear function of the radiation history along an air parcel s trajectory with no apparent sensitivity to the chlorophyll concentration of the surface waters that the air mass interacted with this latter observation contradicts expectations and suggests a simple radiation limitation for the combined direct and indirect marine ocs emissions because the concentration of ocs in the marine boundary layer is so strongly influenced by an air parcel s history marine and atmospheric concentrations would rarely be near equilibrium and thus even if marine production rates are held constant at a given location the ocean atmosphere flux would be sensitive to changes in atmospheric circulation alone we hypothesize that changes in atmospheric circulation including latitudinal shifts in the storm tracks could affect the marine flux through this effect

ion microprobe uranium lead dating of zircons from the lappajarvi impact crater western finland the lake lappajarvi impact crater lies in paleoproterozoic svecofennian metasedimentary rocks on the western side of the central finland granitoid complex 1 9 ga two conflicting ages have been reported for the meteorite impact an age of 77 3 0 4 ma on the basis of ar ar whole rock data from impact melt samples and a paleomagnetic age of 195 ma during studies on impact crater indicator minerals at lappajarvi zircons with an atypical appearance were found in suevite boulders these zircons seemed to have been affected by impact shock metamorphism and it was considered that they would be good candidates for ion microprobe u pb dating allowing a new and independent age estimate for the impact event at lappajarvi four spot analyses on two black coated zircons plotted close to the upper intercept end of the concordia curve giving an approximate age of 1 8 ga for the source rock seventeen analyses were done on three dull zircon grains showing patchy impact related partial recrystallization most of these data fell fairly well on a single discordia line with intercept ages of 73 3 2 5 3 ma and 1854 2 5 1 ma however five of the data spots near the lower intercept end fell on the younger side of the line this was interpreted to indicate post impact loss of lead importantly the new ion microprobe u pb age of 73 3 f 5 3 ma is in a very good agreement with the previously reported ar ar age

morphology of ionospheric f2 region variability associated with sudden stratospheric warmings the effect of sudden stratospheric warming ssw on the f2 region ionosphere has been extensively analyzed for the major event of year 2009 apart from a few reports on other major and minor events morphology of ionospheric responses during ssw can be better comprehended by analyzing such warming events under different solar geomagnetic and meteorological conditions we investigate the features of f2 region variability following the ssw events of 2010 2011 2012 2013 2014 2015 and 2016 using ionosonde data from the asian region covering a broad latitudinal range from 26 6 n to 45 1 n we find perceptible ionospheric variations in electron densities during these warming events which is accompanied by a large variation of 117 within enhancements as compared to a meagre variation of 11 within depressions during these events we also examine six months data at these latitudes and longitudes and find that the maximum and minimum variation in f2 layer critical frequency is observed during each ssw period the influence of quasi stationary 16 day planetary waves is seen during these ssw events further a recently proposed parameter ssw integrated strength by vieira et al 2017 to characterize ssw event with respect to ionosphere is also examined it is seen that it does not fit well for these seven ssw events at these latitudes and longitudes

evaluating the influence of meteorite impact events on global potassium feldspar availability to the atmosphere since 600 ma potassium feldspar present in global mineral aerosol 30 by combining crater size and tectonic reconstructions we are able to provide a quantitative and self consistent assessment of changes to global potassium feldspar availability considerable differences in potassium feldspar availability following meteorite impact events are revealed different impact events generated dust containing different amounts of potassium feldspar differing levels of influence upon climate are hypothesized and should now be tested by looking at stratigraphic records of these events to reveal the sensitivity of climate to different dust mineralogy supplementary material figures showing palaeolatitude determinations using various methods and reconstruction models and estimates of alkali feldspar abundance and distribution across contemporary continental landmasses for meteorite impact events are available at https doi org 10 6084 m9 figshare c 4253312

preearthquake anomalous ionospheric signatures observed at low mid latitude indian station delhi during the year 2015 to early 2016 preliminary results we have analyzed five major earthquake events measuring greater than 6 on richter scale m 6 that occurred during the year 2015 to early 2016 affecting indian region ionosphere using f 2 layer critical parameters f o f 2 h m f 2 obtained using digisonde from a low mid latitude indian station delhi 28 6 degrees n 77 2 degrees e 19 2 degrees n geomagnetic latitude 42 4 degrees n dip normal day to day variability occurring in ionosphere is segregated by calculating f 2 layer critical frequency and peak height variations delta f o f 2 h m f 2 from the normal quiet time behavior apart from computing interquartile range we find that the ionospheric f 2 region across delhi by and large shows some significant perturbations 3 4 days prior to these earthquake events resulting in a large peak electron density variation of similar to 200 these observed perturbations indicate towards a possibility of seismo ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events it was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone as given by dobrovolsky et al 1979 the thermosphere neutral composition o n 2 as observed by global ultraviolet imager across delhi during these earthquake events does not show any marked variation further the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event

midlatitude ionospheric responses to the 2013 ssw under high solar activity ionospheric responses to sudden stratospheric warming ssw are not well understood particularly in the midlatitudes and under high solar conditions during the 2013 ssw ionospheric disturbances were observed in eight locations on the meridional chain from 30 5 degrees n to 42 8 degrees n in northern china the midlatitude ionosphere responded strongly to the ssw despite being under high solar flux the f 2 layer maximum electric density increased by more than 80 and the peak height was elevated more than 60km well set and organized semidiurnal variations were recorded in early and middle january during the ssw in eight observation locations the expected f o f 2 decrease in the afternoon hours was not clearly discernible however nighttime enhancements occurred frequently the time period spectra of the average f o f 2 and zonal winds and meridional winds at altitudes of 86 95km presented quasi 16day planetary wave like oscillations during the warming event the coupling between the atmosphere and ionosphere may be strengthened by the quasi 16day waves the amplified diurnal semidiurnal and terdiurnal tides in f o f 2 were also recorded during the warming in good agreement with earlier observations importantly the variations in the semidiurnal tides included a 16day periodic component indicating that the modulated semidiurnal tides may transmit these 16day planetary wave like oscillations to the f region through wind dynamo although the pw tide interaction theory is not novel it is of significance in the midlatitude ionospheric response to ssw

carbonyl sulfide concentrations in the surface waters and above the pacific ocean we measured the concentration of carbonyl sulfide ocs in the marine atmospheric boundary layer and in the surface layer of the equatorial and northern pacific ocean on two oceanographic cruises during may and june of 1982 and during march may of 1983 our measurements of the mean concentration of atmospheric ocs are 502 21 parts per trillion ppt on the 1982 cruise and 511 19 ppt on the 1983 cruise we found surface water ocs concentrations to range upward from 0 3 stp nl l 1 to a few cases over 3 0 stp nl l 1 we estimate the global mean supersaturation ratio of ocs in seawater to range from 1 5 to 3 0 indicating a global source of ocs from the ocean of 0 2 to 0 4 tg yr 1 we have made laboratory measurements of the dimensionless henry s law coefficient of solubility h the concentration of ocs in air divided by its concentration in 34 90 per mil salinity seawater we found ln h 12 722 0 082 3 496 24 t with no evidence for nonlinearities in the solubility at ambient atmospheric concentrations of ocs

a statistical analysis of the propagating quasi 16 day waves at high latitudes and their response to sudden stratospheric warmings from 2005 to 2018

rock magnetic and paleomagnetic study of the keurusselka impact structure central finland abstract there are 31 proven impact structures in fennoscandia one of the most densely crater populated areas of the earth the recently discovered keurusselka impact structure 62 08 n 24 37 e is located within the central finland granitoid complex which formed 1890 1860 ma ago during the svecofennian orogeny it is a deeply eroded complex crater that yields in situ shatter cones with evidence of shock metamorphism e g planar deformation features in quartz new petrophysical and rock magnetic results of shocked and unshocked target rocks of various lithologies combined with paleomagnetic studies are presented the suggested central uplift with shatter cones is characterized by increased magnetization and susceptibility the presence of magnetite and pyrrhotite was observed as carriers for the remanent magnetization four different remanent magnetization directions were isolated 1 a characteristic svecofennian target rock component a with a mean direction of d 334 8 i 45 6 95 14 9 yielding a pole plat 51 1 plon 241 9 a95 15 1 2 component b d 42 4 i 64 1 95 8 4 yielding a pole plat 61 0 plon 129 1 a95 10 6 3 component c d 159 5 i 65 4 95 10 7 yielding a pole plat 21 0 plon 39 3 a95 15 6 and 4 component e d 275 5 i 62 0 95 14 4 yielding a pole plat 39 7 plon 314 3 a95 19 7 components c and e are considered much younger possibly neoproterozoic overprints compared with the components a and b the pole of component b corresponds with the 1120 ma pole of salla diabase dyke and is in agreement with the 40ar 39ar age of 1140 ma from a pseudotachylitic breccia vein in a central part of the structure therefore component b could be related to the impact and thus represent the impact age

ionospheric response to the 2009 sudden stratospheric warming over the equatorial low and middle latitudes in the south american sector the present study investigates the ionospheric total electron content tec and f layer response in the southern hemisphere equatorial low and middle latitudes due to major sudden stratospheric warming ssw event which took place during january february 2009 in the northern hemisphere in this study using 17 ground based dual frequency gps stations and two ionosonde stations spanning latitudes from 2 8 n to 53 8 s longitudes from 36 7 w to 67 8 w over the south american sector it is observed that the ionosphere was significantly disturbed by the ssw event from the equator to the midlatitudes during day of year 26 and 27 at 14 00 ut the tec was two times larger than that observed during average quiet days the vertical tec at all 17 gps and two ionosonde stations shows significant deviations lasting for several days after the ssw temperature peak using one gps station located at rio grande 53 8 s 67 8 w midlatitude south america sector it is reported for the first time that the midlatitude in the southern hemisphere was disturbed by the ssw event in the northern hemisphere

quiet time variability of the gps tec and eej strength over indian region associated with major sudden stratospheric warming events during 2005 2006 1 this paper describes the quiet time variabilities of the ionospheric total electron content tec derived from the signals from global positioning satellite system gps recorded at several stations in india along with simultaneous observations of equatorial electrojet eej strength obtained from geomagnetic field variations during january march 2006 when sudden stratospheric warming ssw events occurred analysis of the observations presented here confirms that strong correlation exists among the variabilities in eej strength and gps tec observations investigations suggest that there exist large scale wave like structures with periodicity of quasi 16 day wave in the tec observations near the equatorial ionization anomaly eia crest quite similar to that of eej strength our observations also indicate the existence of morning enhancement and evening reduction of tec and eej strength and vice versa during ssw events similar to that reported elsewhere using these observations it is suggested that the quiet time variabilities seen in the gps tec over eia could be caused due to the nonlinear interaction of upward propagating planetary waves pws with atmospheric tides presence of similar periods in the eej strength and tec observations near the eia crest region supports the view that the large scale wave like structures seen in tec near the eia crest are associated with pws that are modifying the primary eastward electric field in the equatorial e region and hence the eej strength through non linear interactions with atmospheric tides

equatorial electrodynamics and neutral background in the asian sector during the 2009 stratospheric sudden warming using ground observations of total electron content tec and equatorial electrojet eej in the asian sector along with plasma and neutral densities obtained from the champ satellite we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major stratospheric sudden warming ssw in january 2009 our analysis reveals the following prominent features first the tec response in tropical regions is strongly latitude dependent with monotonic depletion at the dip equator but a semidiurnal perturbation at low latitudes second the tec semidiurnal perturbation possesses a significant hemispheric asymmetry in terms of onset date and magnitude it starts on the same day as the ssw peak in the northern hemisphere but 2 days later in the southern hemisphere its magnitude is twice as strong in the north than in the south third strong counter electrojet occurs in the afternoon following the strengthening of the eastward eej in the morning fourth semidiurnal perturbation in both tec and eej possesses a phase shift at a rate of about 0 7 h day comparisons with results reported in the peruvian sector reveal clear longitude dependence in the amplitude and hemispheric asymmetry of the semidiurnal perturbation finally thermospheric density undergoes 25 decrease at low latitudes in the afternoon local time sector during the ssw indicating significant cooling effects in the tropical upper thermosphere

the supersaturation of carbonyl sulfide in surface waters of the pacific ocean off peru carbonyl sulfide cos was found to be supersaturated by a factor averaging 2 6 with respect to the atmosphere in surface waters of the continental shelf of peru the degree of supersaturation was correlated with dissolved dimethyl sulfide dms concentrations indicating a possible biogenic source of atmospheric cos the oceanic source of cos could account for a substantial fraction of the cos flux to the atmosphere

attribution of ionospheric vertical plasma drift perturbations to large scale waves and the dependence on solar activity 1 in this study we quantify the contribution of individual large scale waves to ionospheric electrodynamics and examine the dependence of the ionospheric perturbations on solar activity we focus on migrating diurnal tide dw1 plus mean winds migrating semidiurnal tide sw2 quasi stationary planetary wave one qspw1 and nonmigrating semidiurnal westward wave one sw1 under northern winter conditions when qspw1 and sw1 are climatologically strong from thermosphere ionosphere mesosphere electrodynamics general circulation model simulations under solar minimum conditions it is found that the mean winds and dw1 produce a wave two pattern in equatorial vertical e bdrift that is upward in the morning and around dusk the modeled sw2 also produces a wave two pattern in the ionospheric vertical drift that is nearly a half wave cycle out of phase with that due to mean winds and dw1 sw1 can cause large vertical drifts around dawn while qspw1 does not have any direct impact on the vertical drift wind components of both sw2 and sw1 become large at middle to high latitudes in the e region and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift likely through modulating the e region wind dynamo the most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk reflecting the more dominant role of large f region pedersen conductivity and of the f region dynamo under high solar activity therefore the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions not only because variability is more identifiable in a quieter background but also because the e region wind dynamo is more significant these numerical experiments also demonstrate that the amplitudes phases and latitudinal and vertical structures of large scale waves are important in quantifying the ionospheric responses

effect of sudden stratospheric warming on lunar tidal modulation of the equatorial electrojet 1 using the equatorial electrojet eej peak current intensity as deduced from champ magnetic observations from the years 2001 through 2009 we investigated the relationship between sudden stratospheric warming ssw and lunitidal signatures in the tropical ionosphere there is a practically one to one correspondence between midwinter ssw periods and the strongest 13 day modulation of the eej strength as observed by champ that is all the midwinter ssw periods from december 2001 to august 2009 were accompanied by an enhanced 13 day modulation of the eej strength no other geophysical phenomenon brought about as strong a 13 day modulation as those of the midwinter ssw periods during each midwinter ssw period the amplified 13 day modulation of the eej strengths starts roughly within 1 week around the first peak in stratospheric temperature difference an oscillation with a period of 13 26 days is predicted by the lunitidal equation when considering the precession of the champ orbit when fitting the lunitidal equation to the eej modulations during the midwinter ssw periods consistent phase delays of 4 4 0 3 days of the tidal signal emerge for all the cases the results suggest that the pronounced 13 day modulation of the eej strength is related to an enhancement of the lunar tide in the ionosphere by the ssw effect