Out of the 21 days of simultaneous scintillation observations at a chain of stations extending from near equator to about 23°N magnetic latitudes, only on 7 days scintillations could be observed up to about 23° magnetic latitudes (i.e., of Kurukshetra) and on 13 days up to about 21°N (i.e., up to Delhi). However, near the equatorial location Bangalore (magnetic latitude 3°N) scintillations were observed daily except on one day (i.e., on February 16, 1980), when there was a partial solar eclipse during evening hours and it was magnetically disturbed day. On that day there were no scintillations at any of the stations. As mentioned above in section 2, the occurrence and growths of plasma bubbles are studied in terms of scintillation onset times at different latitudes starting from the lowest station Bangalore moving northwards to higher latitudes. Figures 3a, 3b, 3c, and 3d are four examples showing the onsets of four individual plasma bubbles observed on 21- 2-1980, 11-2-1980, 15-2-1980, and 17-2-1980, respectively, and also their subsequent latitudinal/altitudinal growth with local time. In the first two cases (see Figures 3a and 3b), scintillation occurred at all the stations from Bangalore (magnetic latitude 3.0°N) up to Kurukshetra (magnetic latitude 22.8°N) indicating that the plasma bubble and associated irregularities mapped up to 1270 km in altitudes over the magnetic equator whereas, in the next two cases (see Figures 3c and 3d) the bubble could reach only up to the altitude of 710 km as scintillations were observed up to Nagpur (magnetic latitude 12.0°N). Figure 3a shows a case of very rapidly rising bubble which takes less than an hour to rise between 450 km to 1270 km, whereas Figure 3b shows a case of comparatively slow rising bubble which takes almost double the time to rise over the same altitudes range over the magnetic equator. In these figures, bubble rise velocities over the magnetic equator are also given which are derived using successive time delay in the occurrence of scintillations at different locations and the altitudinal separation between their respective field lines over the magnetic equator [Dabas and Reddy, 1990] for different altitudinal slabs. The detailed results about plasma bubble rise velocity, i.e., their estimation; variations with altitudes and correlation with ExB etc. are given in a separate paper by Dabas and Reddy . It is to be pointed out here that a rising plasma bubble also drift (usually) eastward in such a way that their eastward velocity increases as they grow vertically upward. In the Indian sector, using 4 GHz scintillation observations (as mentioned in section 2 above) from two INSAT satellites separated by 20 degrees in longitude and at two stations, one near equator and another at low latitude near Delhi, the average values of eastward drift velocity reported by Dabas et al.  were of the order of 100 to 175 m/s near F region, i.e., around 400 km altitude and of the order of 60 to 90 m/s in the topside ionosphere, i.e., around 1200 km altitude. While calculating the plasma bubble rise velocity (as shown in Figures 3a to 3d) the effect of bubble eastward drift velocity has not been incorporated and hence there can be a systematic error in the calculated rise velocities depending upon the observed time delays between the onsets of scintillations at successive stations. The larger the time delay, the more will be the error. The observed time delay between the onsets of scintillation at Bangalore and Hyderabad was minimum (varies from a few minutes to a maximum of about 10 min), and hence the error introduced by horizontal drift in calculating the initial plasma bubble rise velocity should also be minimum as compared to the other altitudinal slabs shown in Figures 3a to 3d. Here our main objective is to examine the role of initial plasma bubble rise velocity on the altitudinal/latitudinal growth of plasma bubble. In general, results of Figures 3a and 3b suggest that the bubble rise velocity over the magnetic equator decreases with altitudes and seems to be at a maximum near the peak of F region. The two examples shown in Figures 3a and 3c are cases of very rapidly rising bubble where initial plasma bubble rise velocity was more than 400 m/s, and on both these days evening hours h′F was more than 500 km with dh′F/dt greater than 30 m/s. However, still in the first case the bubble rises up to 1270 km in altitude over the magnetic equator reaching up to Kurukshetra latitude, whereas in the second case it was confined up to about 700 km, i.e., up to Nagpur latitude only. In Figure 3b the initial rise velocity (208 m/s) is lower than that of the case shown in Figure 3d (333 m/s), but still in the former scintillations are observed at all the stations, and in the later case these are again confined up to Nagpur only. In these cases also evening hours h′F was more than 450 km with dh′F/dt greater than 25 m/s. The results of the above examples show that the maximum vertical growth, i.e., up to 1270 km (or the latitudinal extent up to Kurukshetra magnetic latitude of 22.8°N) of an individual plasma bubble does not depend only on the initial plasma bubble rise velocity, h′F and ExB as is evident from Figures 3a to 3d, but there seems to be some other contributing factor as well, e.g., the development of postsunset equatorial ionization anomaly (PEA) as indicated by the occurrence of PSSM in IEC suggested by Whalen , which will be examined in detail in the following sections.