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Background: Professional boxing is a popular contact sport with a high risk for both acute and chronic traumatic brain injury (TBI). Although rare, many boxers have died in the ring or soon after the completion of a bout. The most common causes of death in these cases are usually acute subdural hematomas, acute epidural hematomas, a subarachnoid haemorrhage, an intracranial haemorrhage or Second Impact Syndrome (SIS). Ringside physicians are entrusted with the health and safety of boxers in the ring and in the immediate aftermath of a bout.Discussion: As per the Uniform Boxing Rules (approved August 25, 2001, Amended August 2, 2002, Amended July 3, 2008, Amended July 24, 2012, Amended July 29, 2014), the referee is the sole arbiter of a bout and is the only individual authorised to stop a contest. [1]In some states in the United States and in other countries around the world, the referee and the ringside physician are the sole arbiters of a fight and the only individuals authorised to enter the fighting area at any time during the competition and also authorised to stop a fight. This raises the important question of when should a fight be stopped on medical grounds.Conclusion: Standardising medical stoppage decisions in boxing will help to protect a boxer’s health and safety in the ring. Good practice guidelines for medical stoppage due to suspected TBI are suggested. It is recommended that the medical community debate the proposed guidelines vigorously, in order that evidence-based guidelines can be developed in conjunction with professional boxing governing bodies.Keywords: safety, concussion, knockout, traumatic brain injury, contact sports

Published values of Total Electron Content (TEC) measured by ATS-6 are used to assess the latest available IRI-2007 model during solar minimum over Indian sector covering equatorial to low-mid-latitudes stations. The study reveals that during all seasons and at all locations, in general, the TEC predicted by NeQuick and IRI01-corr options provided in the IRI-2007 model shows much better agreement with the TEC observations as compared to those generated by IRI-2001.option. TEC predicted using NeQuick option found to be little more closer to the observation except at equatorial station during daytime, while IRI-2001 option highly overestimates the TEC in all seasons and times.

Modern digital ionosonde measurements at low–middle latitude station, New Delhi, India, are used to assess the IRI-2007 model for the bottomside profile shape parameters B0 and B1 during solar minimum. Comparative analysis shows that in general, the IRI (B0 Table) option reveals better agreement with the B0 observations during daytime in all the seasons, while outside this time period, the IRI (Gulyaeva) predicted B0 values are closer to the observations. For B1 parameter, both the options in the IRI reproduce similar diurnal variations in all the seasons and are closer to observed values except during pre-sunrise and post-sunset hours.

Bottomside electron density (Ne-h) profiles during midday (10–14 h) are analyzed using modern digital ionosonde observations at a low-middle latitude station, New Delhi (28.6N, 77.2E, dip 42.4N), for the period from January 2003 to December 2003, pertaining to moderate solar activity (MSA). Each individual profile is normalized with respect to the peak height and density (hmF2, NmF2) of the F2-region. These profiles are compared with those obtained from the International Reference Ionosphere (IRI-2001) model. Bilitza [Bilitza, D. International Reference Ionosphere 2000. Radio Sci. 36 (2), 261–275, 2001] using both the options namely: Gulyaeva’s model [Gulyaeva, T.L. Progress in ionospheric informatics based on electron density profile analysis of ionograms. Adv. Space Res. 7 (6) 39–48, 1987] and B0 Tab. option [Bilitza, D., Radicella, S.M., Reinisch, B.W., Adeniyi, J.O., Mosert Gonzalez, M.E., Zhang, S.R., Obrou, O. New B0 and B1 models for IRI. Adv. Space Res. 25 (1), 89–95, 2000]. The study reveals that during summer and equinox, the IRI model with B0 Tab. option in general, produces better agreement with the observed median profiles, while the IRI predictions using Gulyaeva’s option, overestimate the electron density distribution at all the heights below the F2-peak. However, during winter, in general, the IRI model, using both the options, reveals shows fairly good agreement with the observations.

Based on cycles 17 – 23, linear correlations are obtained between 12-month moving averages of the number of disturbed days when Ap is greater than or equal to 25, called the Disturbance Index (DI), at thirteen selected times (called variate blocks 1, 2,… , each of six-month duration) during the declining portion of the ongoing sunspot cycle and the maximum amplitude of the following sunspot cycle. In particular, variate block 9, which occurs just prior to subsequent cycle minimum, gives the best correlation (0.94) with a minimum standard error of estimation of ± 13, and hindcasting shows agreement between predicted and observed maximum amplitudes to about 10%. As applied to cycle 24, the modified precursor technique yields maximum amplitude of about 124±23 occurring about 45±4 months after its minimum amplitude occurrence, probably in mid to late 2011.

This paper deals with the diurnal and seasonal variations of height of the peak electron density of the F2-layer (hmF2) derived from digital ionosonde measurements at a low–middle-latitude station, New Delhi (28.6°N, 77.2°E, dip 42.4°N). Diurnal and seasonal variations of hmF2 are examined and comparisons of the observations are made with the predictions of the International Reference Ionosphere (IRI-2001) model. Our study shows that during both the moderate and low solar activity periods, the diurnal pattern of median hmF2 reveals a more or less similar trend during all the seasons with pre-sunrise and daytime peaks during winter and equinox except during summer, where the pre-sunrise peak is absent. Comparison of observed median hmF2 values with the IRI during moderate and low solar activity periods, in general, reveals an IRI overestimation in hmF2 during all the seasons for local times from about 06 LT till midnight hours except during summer for low solar activity, while outside this time period, the observed hmF2 values are close to the IRI predictions. The hmF2 representation in the IRI model does not reproduce pre-sunrise peaks occurring at about 05 LT during winter and equinox as seen in the observations during both the solar activity periods. The noontime observed median hmF2 values increase by about 10–25% from low (2004–2005) to high solar activity (2001–2002) during winter and equinox, while the IRI in the same time period and seasons shows an increase of about 10–20%. During summer, however, the observed noontime median hmF2 values show a little increase with the solar activity, as compared to the IRI with an increase of about 12%.

Diurnal and seasonal variations of bottom side electron density profile shape parameters B0, B1, representing the bottom side F2-layer thickness and shape, are examined using modern digital ionosonde observations at a low-middle latitude station, New Delhi (28.6 ° N, 77.2 ° E, dip 42.4 ° N) for high solar activity (HSA) (2001–2002). Median values of these parameters are obtained at each hour during different seasons and compared with the predictions of the latest version of the international reference ionosphere (IRI), IRI-2001 model using both the options namely: IRI (Gulyaeva) and IRI (B0 Tab.). Results show in general, a large variability in B0, and B1 parameters during all the seasons, the variability is larger during nighttime than by daytime. The diurnal variation of median B0, in general, show more or less similar trends with diurnal maximum occurring around noontime, except during summer, when it occurs between 09 and 10 LT. Variation pattern of B1 in general, is identical in all the seasons with lower values of B1 by daytime than by night. Comparative studies of B0 with those obtained with the IRI model show that in general, IRI (B0 Tab.) option reveals better agreement with the observations during all the seasons for local times from about 10 LT to about 16 LT, while outside this time period IRI (Gulyaeva) matches well with the observations. The predicted B1 parameter, using IRI (B0 Tab.) is close to observations in terms of diurnal variation, while B1 using IRI (Gulyaeva) option, assumes a fixed value of 3 at all local times irrespective of season.

In this paper, the variability of F2-layer critical frequency foF2 is examined, using modern digital ionosonde observations at a low-middle latitude station, New Delhi (28.6°N, 77.2°E, Dip 42.4°N). Data used for the present study are the hourly values of foF2 for the periods of high (2001–2002) and low (2004–2006) solar activity. To investigate the foF2 variability, the values of median, lower quartile and upper quartile are estimated at each hour for different seasons, during both the solar activity periods. The variability index (henceforth referred to as VI) of foF2 is then obtained by using inter-quartile difference and its percentage ratio to the median. Results show that VI is in general, lower during daytime hours than by night during high solar activity for all the seasons, while during low solar activity, VI behavior is irregular during all the seasons. A solar activity dependence of VI is found with maximum values during periods of low solar activity in all the seasons except for winter during pre-dawn and post-sunset hours. Comparisons of observations with IRI-2001 model [Bilitza, D. International Reference Ionosphere 2000. Radio Sci. 36 (2), 261–275, 2001] show in general good agreement during both the solar activity periods, with model values lying within inter-quartile range.

Using digital ionosonde observations at a low mid-latitude station, New Delhi (28.6°N, 77.2°E, dip 42.4°N), we have derived hourly monthly values of hmF2 (the real height corresponding to the peak electron density in the F2-region), employing both the Dudeney (1983) and Bilitza (1990) empirical formulations for the period from January 2001 to August 2002. The diurnal and seasonal variations of hmF2 are analyzed. Further, to assess the predictability of the latest available model, International Reference Ionosphere, (IRI-2001), we have obtained the median values of hmF2 derived from M(3000)F2 for each hour during different seasons and compare these with the model. Our results show that both the Dudeney (1983) and Bilitza (1990) formulations reveal more or less a similar diurnal trend of hmF2, with higher values around midnight and lower during sunrise, in all the seasons. It is also noted that the hmF2 shows a larger variability around midnight than by daytime, in all the seasons. Further, the study shows that median values of observed hmF2, using both formulations, are somewhat larger than those predicted by the IRI, in all seasons and at all local times. During summer, the IRI values agree comparatively well with the observations, especially during daytime. Major discrepancies occur when the IRI underestimates observed hmF2 for local times from about 14:00 LT to 18:00 LT and 04:00 LT to 05:00 LT during winter and equinox, where the percentage deviation of the observed hmF2 values with respect to the IRI model varies from 15 to 25%. The difference between the model and observations, outside this time period, remains less than 20% during all the seasons. Key words. Ionosphere (modelling and forecasting; equatorial ionosphere)

Incoherent scatter radar data from Arecibo, for high solar activity (HSA) (1989–1990) as well as for low solar activity (LSA) (1974–1977) periods, are used to study the seasonal and solar activity variations in electron temperature ( T e ) for noontime conditions. Inspite of large day-to-day variations, clear seasonal variations in average T e can be identified for both solar activity periods, with winter temperatures significantly higher in the topside (400–700 km) ionosphere. Further, comparison of average T e profiles for each season reveals distinct solar activity variations – a large increase in the F-region (200–350 km) T e , during summer and equinox as compared to winter, occurs as one moves from low to HSA. In the topside, however, electron temperature changes little with solar activity. Comparisons with IRI-95 and Truhlik et al. (2000) models show a reasonable agreement within one standard deviation of the measured values.

It is now well known that in the topside ionosphere thermal conduction from the protonosphere becomes the dominant factor over the heating and loss terms in shaping the ionospheric electron temperature ( T e ) profile. By analyzing a limited database of incoherent scatter (IS) T e measurements, Mahajan and Pandey [J. Geophys. Res. 85 (1980) 213] reported a correlation between the electron heat flux and electron density in the topside ionosphere. Since attention has been steadily mounting for the empirical modeling of T e , we now exploit the large database of IS measurements of T e and N e at Arecibo during 1989–1990 (high solar activity), as well as during 1975–1976 (low solar activity) for this purpose. We again find a functional relationship between heat flux and electron density in the topside ionosphere during both the solar activities. These functional relationships are used to generate topside T e profiles.

Using digital ionosonde observations at low-latitude station, Delhi (28.6 N, 77.2 E, mag. dip 42.4 N), the diurnal and seasonal variations of the critical frequency of F2 layer (foF2) are analyzed from August 2000 to July 2001 during a high solar activity period. Also, noontime bottomside electron density (Ne-h) profiles, below the F2-peak, are derived from ionogram, using the POLAN (Report UAG-93, WDC-A, for Solar Terrestrial Physics, Boulder, Co.) program during the same period, and these profiles are then normalized to the peak height and density (hmF2, NmF2) of the F2-region. These observations are used to assess the predictability of the International Reference Ionosphere, IRI-2000 model (Radio Sc. 36(2) (2001) 261). Results show in general, a large variability, (1σ, σ is standard deviation), in foF2 during nighttime than daytime during winter and equinox, the variability of foF2 about the mean is about ±25% by night and ±15% by day. The IRI model shows a fairly good agreement with foF2 observations during daytime, however during nighttime, the discrepancies between the two exist. Comparative studies of the normalized observed profiles with those obtained with the IRI model (Bilitza, 2001) using both the options namely: Gulyaeva's (Adv. Space Res. 7 (1987) 39) model and B0-Table (Adv. Space Res. 25(1) (2000) 89), show that during all the seasons, in general, the B0-Tab option, reveals a better agreement with the observations, while the IRI model using Gulyaeva's option, overestimates the electron density distribution during summer and equinox, however, during winter, the model is close to the observations. The comparisons of average profile shape parameters (B0,B1) derived from noontime observed profiles, with those obtained, using B0-Tab option, in the IRI model, show a good agreement during all the seasons. However, B0, B1 obtained, using Gulyaeva's option in the IRI model, show a disagreement with the derived B0, B1 values during all the seasons, except during winter, for B0 parameter.

We have used about 16000 high resolution electron density profiles from Arecibo (18.4 N, 66.7 W, dip 50°) incoherent scatter radar for the years 1974–1977 and 1989–1990 to study the control of solar activity on the F2 peak height (hmF2). Although the general trend of diurnal variations in hmF2 are nearly identical (i.e. maximum around midnight and minimum around sunrise) during low as well as high solar activity, the median hmF2 increases by about 100 km from solar minimum to solar maximum. Further, there is a considerable day-to-day variability in hmF2. Comparison of measured hmF2 with the IRI (derived from numerical map of M(3000)F2) reveals that IRI generally overestimates this parameter during low solar activity and underestimates during high solar activity.

Measurements of electron density profiles carried out at the low latitude station Arecibo, with the incoherent scatter radar, are used to derive total electron content (TEC). Comparisons are made with the IRI-95 model. Some discrepancies are found between the observed and the IRI predicted TEC and these discrepancies are maximum in equinox and summer months and minimum in winter months. However, for winter, a fair agreement is found between the IRI and the Arecibo data. We attribute these discrepancies to the profile shapes in the IRI model.

In order to check its usefulness for the IRI, incoherent scatter (I.S.) radar measurements at Arecibo (18.4° N, 66.7° W), for the solar minimum period of 1974–1977 are used to study equivalent slab thickness (EST) and its variability. While systematic diurnal changes are apparent, day-to-day and hour-to-hour fluctuations can also not be overlooked. This variability is examined in relation to the simultaneously measured F-layer peak height and electron temperature. While during nighttime, EST shows dependence upon the F-layer peak height (hmF2), it shows by day a dependence on electron temperature.

High resolution electron density profiles (Ne), measured with the Arecibo incoherent scatter radar (I.S.), are used to obtain the “best fit” bottomside parameters B0 and B1 by comparing the observed profiles with the IRI bottomside profile function. For each profile, the comparison is done for all heights between hmF2 and h0.24 - the altitude where density falls off to quarter of the peak value. However, when a F1 ledge is present, the comparison is limited to altitudes between hmF2 and hmF1. A large ‘day-to-day’ and hour-to-hour variability is seen in both B0 and B1. Median values of these parameters are used to generate empirical models. Comparisons are also made with the IRI model.

Based on earlier Ionosonde and Rocket data IRI-1996 assumes a constant hmE value of 110 km throughout. Though agreeing in the average with that value, incoherent scatter radar (I.S.R.) measurements at Arecibo show a total dispersion of about 15 km and a small diurnal variation with slightly higher values for solar zenith angles greater than 60°.

About 1500 electron density (Ne) profiles observed with the Arecibo incoherent scatter (I.S.) radar have been used to obtain the “best” B0 and B1 parameters by fitting the observed profiles to the IRI bottomside profile function. Seasonal and diurnal variations of these parameters are obtained. The relative difference between the “best fit” profiles and the observed I.S profiles is also studied. This difference is rather small during the night for all the seasons, but is very large during the day, especially during summer and equinox seasons, when an F1 layer is present. About 70 % of the profiles show rather good agreement.

In the IRI model foF2 ‘saturates’ when R12 - the 12 months running mean sunspot numbers - is equal to 150. This is surprising since with increase in sunspot numbers, solar EUV flux would increase, which would enhance the ion production rate. Consequently, foF2 should increase if dynamic effects (i.e, ion drift velocities) do not change significantly with R12. To examine this discrepancy, we analyze ionospheric data from three Indian stations, namely Kodaikanal (10.2°N,77.5°E), Ahmedabad (23.0°N,72.6°E) and Delhi (28.6°N,77.2°E) for 35 years during the solar cycles 19,20 and 21. We find that foF2 does increase with solar activity, though the increase is faster at lower levels and slower at higher levels. We fit 2nd degree polynomials to the foF2/R12 points for each hour of the day for each month and then determine from these polynomial fits the value of R12 at which foF2 saturates. It is seen that foF2 saturates for R12 well above 150 in a very large number of cases, though a few exceptions are also there.

The topside electron density profiles for sunrise and sunset conditions measured with incoherent scatter radar at Arecibo, Puerto Rico, for the period August 1974 to May 1977 are compared with IRI. About 140 Ne-h profiles have been used in the analysis. We have studied the altitude variation of N/NmF2 against (h - hmF2) for sunrise and sunset period covering all seasons. It is observed that for sunrise conditions the IRI overestimates the topside electron density during all seasons. During sunset conditions the IRI also generally overestimates electron density with occasional exceptions. Similar results have earlier been reported for midday and midnight conditions from the Arecibo measurement (Pandey et al., 1996).

The size and shape of the valley region between E and F layers is studied for nighttime conditions by using high resolution electron density profiles measured by the incoherent scatter radar at Arecibo, Puerto Rico, (18.3°N,66.7°W). Important valley parameters like width, depth and height of the valley minimum are derived from these measurements. By combining these nighttime results with our earlier daytime model (Mahajan, et.al , 1994), we now present a model for the full diurnal variation of the E–F valley parameters. Comparison with IRI-90 indicates significant differences between our model and the IRI valley model.

About 2000 electron density height profiles observed with the Arecibo (magn.dip 50°) incoherent scatter radar are used to compare the diurnal and seasonal variations of hmF2 with the IRI-90. A good agreement is seen for the median values. The midday bottomside profiles normalized to the peak density are compared with IRI-90 for each season and it is found that IRI overestimates the electron density distribution in the region 100 km below the F2 peak for equinox and summer but matches well during winter.

Using high resolution electron density (Ne) profiles from Incoherent Scatter (I.S.) measurements at Arecibo, geometric parameters (transition height, scale height) of 4 LAY functions are determined. The median values of the above parameters are obtained for each hour during different seasons and compared with main LAY parameters obtained from IRI-90. It is observed that during all the seasons the transition height parameter of the F2 layer derived from observed profiles agrees well with the parameter obtained from IRI during daytime only, while for nighttime large departures are observed for all seasons. Large seasonal variability is also found in the principal scale parameter related to thickness of F2 layer. The difference between those in observed profiles compared to IRI varies from 38 km to 45 km.

The International Reference Ionosphere provides an option for using the half-density height h0.5 when determining the bottom-side electron density profile. For low latitudes the ratio h0.5/hmF2 (peak height) is modified using Arecibo incoherent scatter electron density profiles. A linear variation with latitude of the coefficients is introduced for nighttime and daytime in case h0.5 is located above the F1 layer heights (class ‘A’). The profile semithickness is large when 0.5NmF2 value is less than NmF1 (class ‘B’). At low latitudes class ‘B’ occurs during the first half of the day; at mid-latitudes, however, the Digisonde data from Millstone Hill show these to occur during most of the daytime.

Observed f0F2 data from ionosonde measurements for three low latitude Indian stations namely Delhi (28.6°N, 77.2°E), Ahmedabad (23.0°N, 72.6°E) and Kodaikanal (10.2°N, 77.5°E) are analysed and compared to the IRI-90. The analysis covers all types of solar activity namely periods of high (R12 = 160), low (R12=15) and medium (R12 = 50) solar-activity for summer and winter. Discrepancies could be attributed to a longitude dependent shift in the latitudinal position of the equatorial anomaly crest towars higher latitudes that occurs with increaseing solar-activity.. This feature is not satisfactorily represented in any of the global options of the IRI.

High resolution electron density profiles, measured with the Arecibo incoherent scatter radar have been used to derive h0.5, the height of the half density point. More than 2400 profiles, for the period August 1974 – May 1977, have been used to study the behaviour of this parameter. Our analysis shows that during the night, h0.5 varies mostly between 200 and 350 km, but during the day the excursion is larger and values lower than 150 km are also seen. These lower values are often coincident with the presence of a layer (F1) between h0.5 and hmF2. We have therefore, divided the daytime data into two classes, class ‘A’ where h0.5 is more than hmF1 and class ‘B’ where h0.5 is less than hmF1. We find that in both the classes, most of the variability in h0.5 is due to the variability in hmF2 and a linear relationship between h0.5 and hmF2 is seen, although the dispersion in class ‘B’ is larger. Within the same class, no difference is seen in the relationship between day and night. We also compare the parameter Y0.5 hmF2 obtained from the Arecibo measurements with that calculated from the IRI-90 model, based upon Gulyaeva's (1987) formula. In class ‘A’ the median values of this parameter vary between 0.15 and 2.0 with no major seasonal differences. The IRI values, however, are significantly larger. On the other hand, class ‘B’ shows larger seasonal differences, particularly between summer and winter, but the discrepancy with the IRI is somewhat smaller.

High resolution electron density measurements from Arecibo incoherent scatter (i.s.) radar are used to make a detailed study of the E-F valley. Features of the important valley parameters like height, width and depth are examined. These features are then compared with the available theoretical and empirical models. The depth of the valley obtained from the empirical models agrees with i.s. measurements for near-noon periods, but disagrees with these measurements for pre-noon and post-noon periods. Further, the i.s. measurements indicate that E-F valley is rather small during daytime as compared to models which give larger width. During the night, the valley is quite wide and deep but the presence of sporadic-E (Es) contaminates the Ne-h profiles observed with the i.s. radar. As a result the valley parameters cannot be determined unambiguously during the night.

[1] The equatorial and low latitudinal F region ionosphere is highly dynamic and unpredictable because of various geophysical mechanisms operating therein. In the present study, two HF prediction models for short and long term are developed for equatorial and low-latitude F region ionosphere. In the first approach, multiple regression analysis (MRA) for the dependence of F region parameters, namely, foF2 and M(3000)F2, on solar 2800 MHz flux (F10) and geomagnetic index Ap are generated, and in the second one, second-degree (SD) coefficients are generated, both by fitting monthly median foF2 and M(3000)F2 with corresponding 12 monthly mean sunspot numbers (R12) using data over three solar cycles. For MRA, daily foF2 and M(3000)F2 values for each hour obtained from Delhi (28.6°N, 77.1°E) digital ionosonde for about half a solar cycle are used. MRA coefficients for foF2 and M(3000)F2 are obtained for every month over 2400 UT times using daily F10 and Ap values separately for quiet (Ap 25) periods. Similarly, SD coefficients are obtained each month at all local times for all the 14 stations covering a geographic latitude range from about 0°N to 45°N. In this way, once appropriate coefficients for each hour for all the 12 months are obtained, they are used by the computer-based MRA and SD models to predict ionospheric hourly foF2 and hmF2 values for given inputs such as month, F10, Ap, and R12, as the case may be. Predicted model values of foF2 and hmF2, calculated on short- and long-term basis, are then compared with the observed data over Delhi and also with those obtained using international reference ionosphere (IRI)-2001 model. From our comparative studies it is observed that MRA and SD models show better agreement with observations compared to the IRI model for both long- and short-term basis and among the two the MRA model provides best agreement with the observed ones, even during the magnetic storm periods. The SD model, on the other hand, which is based on monthly median values, is useful for providing long-term predictions for HF communication applications.

The valley between the E/F-regions was studied with electron density — height profiles from the Arecibo Incoherent Scatter Radar. Our analyses indicate that while the valley is rather small during the day it is very deep and wide during the night. No significant changes in the valley parameters were seen during the day but large changes occurred during the night. Intermediate layers also appear between the E and F regions during the night.

Model calculations, as well as optical observations, have shown that hot oxygen is the dominant neutral constituent up to about 3000 km in the upper atmosphere of Venus. Consequently O+ is expected to be the dominant ion up to about 3000 km in the upper ionosphere of Venus. Under normal circumstances, it is difficult to verify this result, since the solar wind interaction terminates the Venus ionosphere at altitudes below about 500 km for subsolar conditions. However, the upper boundary of the Venus ionosphere can move up to very high altitudes during some rare events when the solar wind dynamic pressure is extremely low. An analysis of Pioneer Venus measurements during such events indeed shows O+ to be the dominant ion at altitudes even as high as 2800 km. This result provides ionospheric evidence of hot oxygen in the upper atmosphere of Venus.

The Pioneer Venus Orbiter (PVO) had on board the electron temperature probe experiment which measured temperature and concentration of electrons in the ionosphere of Venus. When the probe was outside the Venus ionosphere and was in the solar wind, the probe current was entirely due to solar photons striking the probe surface. This probe thus measured integrated solar EUV flux (Ipe) over a 13-year period from January 1979 to December 1991, thereby covering the declining phase of solar cycle 21 and the rising phase of solar cycle 22. In this paper, we examine the behavior of Ipe translated to the solar longitude of Earth (to be called EIpe) during the two solar cycles. We find that total EUV flux changed by about 60% during solar cycle 21 and by about 100% in solar cycle 22. We also compare this flux with other solar activity indicators such as F10.7, Lα, and the solar magnetic field. We find that while the daily values of EIpe are highly correlated with F10.7 (correlation coefficient 0.87), there is a large scatter in EIpe for any value of this Earth-based index. A comparison of EIpe with SME and UARS SOLSTICE Lα measurements taken during the same period shows that EIpe tracks Lα quite faithfully with a correlation coefficient of 0.94. Similar comparison with the solar magnetic field (Bs) shows that EIpe correlates better with Bs than with F10.7. We also compare EIpe with total solar irradiance measured during the same period.

When compared with the CCIR predictions, the observed values of NmF2 and hmF2 over Delhi and Ahmedabad show considerable differences. Comparison of the shape of the bottomside electron density profile obtained by true height analysis and the shape predicted by the interim 1985–1986 version of IRI shows that the observed values are typically lower (by day) than those given by the model in the sub-peak region, but higher below about 200km. The use of a sum of LAY functions to describe the middle ionosphere electron density profile is illustrated with a typical example.