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Abstract. The electron and ion temperature at the lowlatitude ionosphere exhibits a wide variety of fluctuations. Observations using SROSS-C2 satellite RPA payload during 1995-2000 provide an excellent opportunity to study the fluctuations in T e and T i in the upper ionosphere and to understand the dynamic processes existing at those altitudes. The spectral analysis of electron and ion temperatures using Fourier and wavelet techniques reveal the presence of quasiperiodicities, such as 14-day, 19-day, 27-day, 55-day, 154-day, 180-day, 1-year and 1.3-year periods. The daytime and nighttime values of T e and T i exhibit different types of characteristic variations. The wavelet spectrum presented depicts the temporal evolution the power of each periodicity present in the daytime and nighttime values of T e and T i . The time evolution of electron and ion temperatures are compared with that of A p and 10.7 cm solar radio flux, to infer the source of temperature fluctuations at the upper ionosphere.